Time graph. Name_____ In this lab, you will compare and learn the differences between speed, velocity, and acceleration. The journey takes two hours. Velocity vs. Begin by having the students define the terms acceleration and velocity, then have them write down and test their predictions using the toy car and ramp setup described above. Speed is how fast something moves. Pete is driving down 7th street. Speed and Velocity Lab Materials: • Measured area to perform the tests (20 meters) • Stopwatch • 2 Students Procedure: 1. What is the magnitude of the acceleration of an object in free fall near Earth’s surface? 20. Physics Lab 1: Zoooooooom! How fast is fast? by Veronica Davis (Cornell University) Audience: Middle school physical science Objectives • Identify how to determine an object’s speed • Determine lab procedure to calculate an object’s average speed • Understand the difference between speed and velocity Pre-Lab Questions 1. Velocity is a physical vector quantity; both magnitude and direction are needed to define it. Which of the following is a measure of velocity? a. The slope of curve (e) is zero. What was your average speed? Answer: 61 mph 13. Students will know if they made a mistake right away when they notice their answer is not on the answer sheet. 2) where ~x is the position as a function of time, ~v is the velocity as a function of time, ~v0 is the initial velocity, ~x0 is the initial position, t is time and ~a is the constant acceleration. In physics, acceleration is the rate at which the velocity of a body changes with time. This section contains Physics Question with multiple answers. time and distance. vector and they solve 4. docx Unit 3 Day 1. Be sure to show your work for each problem (write the formula, numbers with correct units, and the. Velocity is speed with a direction. (the most difficult for most people) Acceleration. Though this is a classic lab activity, you will appreciate the Get Free Access There are 10 questions that have learners define force, acceleration, velocity, and speed. Velocity is speed in a given direction. For instance, the ideal pedal in a vehicle is known as the accelerator because it's the pedal that could produce the car go faster. A ball rolls down a ramp for 15 seconds. Complete the statements below: A. How far does the train travel? 19. We believe it deliver interesting things for Speed Velocity And Acceleration Worksheet Answer Key As Well As Physics Modeling Unit 2 Constant Velocity. Note: the symbol v can be used to denote speed or velocity, here it is used for speed. What is its average acceleration? 6 m/s2 2. A man moving from 0 to -10 at a fast pace the moving back to 0 at a slow pace. You will ALSO need to review ALL the pages we completed in the lab book so far. Speed is a scalar and velocity is a vector. It is expressed as distance moved (d) per unit of time(t). A man measures the acceleration of an elevator by using a spring balance. Speed, Velocity and Acceleration- Unit with WorksheetsThis unit in the form of pdf file and covers everything from SPEED, VELOCITY AND ACCELERATION, UNITS OF EACH TERMS, TYPES AND CALCULATION THE SPEED, VELOCITY AND ACCELERATION OF AN OBJECT. Speed Velocity And Acceleration Answer Key. Physics Laboratory Report Sample PHY 223 Lab Report Newton's Second Law Your Name: Partner's Full Name(s): We found that for a given force the acceleration of the glider was inversely proportional to the mass of the glider, in agreement with intervals to calculate the average speed of the glider during its pass through each photogate. Velocity is a vector, which means it has both speed and direction. VPL Lab -Dynamics, Acceleration, Freefall 1 Rev 12/19/18 In our constant velocity lab we used the motion sensor to measure the position of an object 100 times a second and plotted constant velocity. or 4 feet, from the back of the boat. We believe it deliver interesting things for Speed Velocity And Acceleration Worksheet Answer Key As Well As Physics Modeling Unit 2 Constant Velocity. A ball rolls down a ramp for 15 seconds. This is the fit. Which of the following are important in measuring motion? a. Your goal in this lab is to learn how to describe various kinds of motion in more detail. Some of the worksheets for this concept are Speed velocity and acceleration calculations work, Speed velocity and acceleration calculations work s, Sp211 work 1 position displacement and, Name key period acceleration problems, Displacementvelocity and. Speed Velocity And Acceleration Lab. Speed Speed is the rate of change of distance. accelerating A runner of going at 10 kilometers per hour. Velocity is the rate of displacement of an object. where t1= 0 seconds D ring the time inter al 0 seconds. Therefore, the velocity and acceleration are zero. Lab Reports: Inquiry into Speed, Velocity, and Acceleration Cars Downhill Practice: SVA Practice Problem Answers SVA Practice Problems Important Terms: Velocity: the speed and direction of an object Acceleration: the rate at which velocity changes Force: a push or a pull one body exerts on another Inertia: the tendency of an object to…. time and distance. The change in velocity can be observed as a change in speed or a change in direction, such as 10 m/s2 east. The difference between scalar and vector quantities is also discussed. Physical Science: Motion: The Relationships between displacement, time, velocity and acceleration: Displacement, Time and Velocity PLO C6 1. Your goal in this lab is to learn how to describe various kinds of motion in more detail. Speed, Velocity and Acceleration Calculations Worksheet Part 1 - Speed Calculations: Use the speed formula to calculate the answers to the following questions. Speed is the absolute value of velocity and velocity is the first derivative of the position function. Helped to highlight the fact that just because an object is accelerating faster, does not mean it is traveling faster. Spring ‘11 Lab 7 –Velocity and Acceleration Sensors Lab 7-4 magnetic gear pickup (MGP) readout (direct reading in RPM). Speed and Velocity Review Worksheet from velocity and acceleration calculation worksheet answer key , source:pinterest. Identify how acceleration, time, and velocity are related. The formal definition of acceleration is consistent with these notions, but more inclusive. Does the initial velocity of an object have anything to do with its acceleration? For example, compared to dropping an object, if you throw it downward would the. This test covers vectors using both polar coordinates and i-j notation, radial and tangential acceleration, and two-dimensional motion including projectiles. A meteoroid changed velocity from 1. Speed Velocity And Acceleration Answer Key. Examine the plot of Velocity versus Time in the Graph display. Watch how the graphs of Position vs. Velocity = (change in displacement / change in time) SI unit: m s-1 Symbol: v or u. For a pendulum which has a light string to hang a bob, I know that when the bob swing to the leftmost or rightmost end, the velocity of the bob is zero and the acceleration should be maximized. Acceleration is different than speed. Set up your Table display so it shows the values of position, velocity, and acceleration. SHOW WORK! Time (sec) Distance (m) 0 50 75 90 110 125 What is the average speed after two seconds? After three seconds? After 5 seconds? What is the average speed between two and four minutes?. This question requires an extended response, ie your answer must. VPL Lab -Dynamics, Acceleration, Freefall 1 Rev 12/19/18 In our constant velocity lab we used the motion sensor to measure the position of an object 100 times a second and plotted constant velocity. When I let the man move at a velocity of 1 meter/sec for two sec. Use data from the graph to estimate the acceleration of the stone as it fell. Know ALSO the following vocabulary terms: Constant speed - Speed that does not change. Helped to highlight the fact that just because an object is accelerating faster, does not mean it is traveling faster. Speed is a scalar, velocity is a vector Constant Acceleration. time graph to calculate distance Filed under: Physics — Tags: distance , velocity — Michael Bray @ 10:02 pm Physics students often overlook a very powerful tool (a velocity vs time graph) when they are trying to calculate distance traveled when given information about velocity and/or acceleration. It will unconditionally ease you to look guide speed velocity and acceleration. Andersen explains the basic quantities of motion. Answers are on the third page. I had to find the acceleration and velocity of the cart as it goes down the incline. • Acceleration (a) - how fast you speed up, slow down, or change direction; the rate at which velocity changes Speed vs. In everyday life, speed is a simpler idea than velocity because it agrees with common sense. 1) How do we KNOW that inertia affects the acceleration of an object? 2) Why is it so important to make sure the balloon was the same size for each test (in the Balloon Rocket lab)? 3) What could have caused the difficulty you experienced in getting the straw to slide down the string smoothly? (more than one thing) 10/21 + 22:. [1] Angular velocity is not transverse velocity. Speed is a scalar quantity with dimensions distance/time. One team member will perform each of the tasks in the table below while the other student records the amount of time it takes to complete each task. 15 Handout 2) Time: 45 - 50 minutes. Describe the shape of the data points. What is the person’s average velocity? Answer: 0 m/s 14. meters due south in 5. You will ALSO need to review ALL the pages we completed in the lab book so far. final velocity was 7 m/sec, what was the acceleration of the ball ? 9. Show the formula used, the setup, and the answer with the correct units. Some of the worksheets displayed are Speed velocity and acceleration calculations work, Displacementvelocity and acceleration work, Time velocity, Velocity and acceleration calculation work, Speed velocity and acceleration calculations work s, Distance time speed practice problems. The three major types of simple linear motion are constant velocity motion, uniformly accelerated linear motion, and free fall. Rotation occurs when the object spins about an internal axis. How to Use LinkedIn Learning. We hope this graphic will be certainly one of good resource for Speed Velocity And Acceleration Worksheet Answer Key As Well As Physics Modeling Unit 2 Constant Velocity. Compare and analyze these numbers to your average acceleration to each point from the first part of the lab. The cart is expected to reach a constant velocity and then continue moving at the same speed along the same direction from then on. This will allow. at2: (3) In this formula, the variables are the same as in the previous equations. Angular speed is the change of rotation per unit time. When I let him move at a velocity of 4 meters/sec for two sec. AP Physics 1 Investigation 1: 1D and 2D Kinematics How is the translational motion of a ball described by kinematics? Central Challenge Students observe a steel ball rolling down an inclined ramp, then across a horizontal track, and finally as a projectile off the end of the ramp onto the floor. Acceleration - a measure of the change in the velocity of an object over a period of time. It will unconditionally ease you to look guide speed velocity and acceleration. time, velocity vs. Thanks for stopping by! I’m Virgil Ricks, and this is 2 minute classroom. It also includes numerous workshee. When you accelerate or decelerate, you change your velocity by a. In this lab you will look at velocity vs. Speed and Velocity Review Worksheet from velocity and acceleration calculation worksheet answer key , source:pinterest. For a pendulum which has a light string to hang a bob, I know that when the bob swing to the leftmost or rightmost end, the velocity of the bob is zero and the acceleration should be maximized. The average speed is the distance (a scalar quantity) per time ratio. Use this exciting lab to help students discover speed, velocity and acceleration and how various motions are represented graphically. Some of the worksheets for this concept are Work 7 velocity and acceleration, Speed velocity and acceleration calculations work, Velocity and acceleration calculation work, Science topic, Displacementvelocity and acceleration work, Physics acceleration. • In the acceleration part of this lab, you will work with a glider, Record all your measurements in your lab book. Parametric Equations - Velocity and Acceleration. you need to speed up to catch up to the other players or to beat the other team to the hoop. In this lab you will learn the difference between speed, velocity, and acceleration. Speed Velocity And Acceleration Answer Key. When you accelerate or decelerate, you change your velocity by a. Velocity and Acceleration Lab Activity. a = ∆v/∆t Angular Momentum - a concept used to describe the spinning momentum of an object. Explore how circular motion relates to the bug's x,y position, velocity, and acceleration using vectors or graphs. Section 6-2 "Speed, Velocity, and Acceleration" Word Problems Part A - Speed, Velocity, Distance, and Time Word Problems - solve the following word problems using the following physics formula's. The purpose of this lab is to create distance-time and speed-time graphs from collected data. Sketch velocity vs. Speed = (change in distance / change in time) SI unit: m s-1 Symbol: v or u. Hypothesis It is hypothesized that the object that is dropped will endure gradual change acceleration in acceleration. Rotation occurs when the object spins about an internal axis. Displaying top 8 worksheets found for - Speed Acceleration. Identify how acceleration, time, and velocity are related. Forces can change the position, shape or motion of an object. speed, velocity b. Angular speed is the change of rotation per unit time. Difference between Speed, Velocity and Acceleration? This movement and the speed of movement have been given some basic terms in Physics. 3-2 QUESTIONS: 1. he had moved about 8 meters. Pete is driving down 7th street. This report must be typed, and any diagrams, figures, or tables should be embedded into the document. The Physics in Motion teacher toolkit provides instructions and answer keys for study questions, practice problems, labs for all seven units of study. If an object is moving downwards, then its velocity is described as being downwards. time graphs relate to motion diagrams and position vs time graphs. Velocity = (change in displacement / change in time) SI unit: m s-1 Symbol: v or u. The cart is expected to reach a constant velocity and then continue moving at the same speed along the same direction from then on. When I let the man move at a velocity of 1 meter/sec for two sec. 30 South c. The data you will take will be time of travel, the length of the trip, and also information that relating to the steepness of the incline of the ramp we use. What is the acceleration of the elevator? Answer:. like velocity, the resultant magnitude (speed) is. But 3 seconds later, at the bottom of the slope, its speed is 22 m/s. Speed, Velocity and Acceleration- Unit with WorksheetsThis unit in the form of pdf file and covers everything from SPEED, VELOCITY AND ACCELERATION, UNITS OF EACH TERMS, TYPES AND CALCULATION THE SPEED, VELOCITY AND ACCELERATION OF AN OBJECT. Speed, Velocity and Acceleration Calculations Worksheet : Speed Calculations: Use the speed formula to calculate the answers to the following questions. Use a velocity vs. Average speed is distance divided by time. A mixture of resources I use for this unit. Calculate the acceleration for the following data. When you accelerate or decelerate, you change your velocity by a specific amount over a specific amount of time (change in velocity over change in time. Movement can be shown in distance-time and velocity-time graphs. Answers are on the third page. What is Speed?. Show the formula used, the setup, and the answer with the correct units. same time interval. Speed, Velocity, and Acceleration Goals: To investigate what is needed to describe motion completely. Define velocity. It tells you the speed that something is travelling, but it also tells you the direction in which SCIENCE: Speed, velocity and acceleration d e f. In the first part of this lab, you will be using "air tracks," which create group the answers to the following questions. For example, an object such as a car that starts from a full stop, then travels in a straight line at increasing speed, is accelerating in the direction of travel. Velocity is used to calculate the time taken for a storm to reach the coastline, time taken for rockets to reach the moon and so on. Although you will work as a team during this lab, each student will turn in their own lab report. Along which path would you have to move with the greatest speed to arrive at the destination in the same amount of time? 2. In this acceleration and average speed activity, students learn the equations for acceleration and average speed. This selection allows you to play with the position, velocity, and acceleration for two objects at the same time. Given an example of an object that has (a) high velocity and low acceleration. The ride consists of seats mounted on each end of a steel beam. Time graph by sliding the points up or down. Speed, Velocity, and Acceleration Problem Use your OWN PAPER, and Show the formula used. Suppose you are in a car moving at (initially) 1 m/s. Speed is a scalar and velocity is a vector. Lab 2: Kinematics and Terminal Velocity October 19, 2006 Introduction Preparation Before coming to lab, you should have read the lab handout on uncertainty and measurement, as well as completed lab 1. What was the weight of the stone on earth? Give the unit. meters due north in 15 seconds. They can make objects speed up, slow down or change direction. Purpose The purpose of this lab was to evaluate the increase in velocity with time during a free fall. Mathematical and graphical models could include distance, displacement, speed, velocity, time, and acceleration. What is speed? What is velocity? Give a definition, in your own words, for both. time and acceleration vs. Velocity Data. What is the acceleration? 7. Learn about position, velocity, and acceleration graphs. Let us take a look at them one by one. It can be used to measure the release velocity during a baseball pitch, the duration of ball-foot contact during a kick, or a sprinter's acceleration coming out of the blocks. For example, an object such as a car that starts from a full stop, then travels in a straight line at increasing speed, is accelerating in the direction of travel. Directions: Use this review sheet as GUIDE as to what you need to know. It is calculated by subtracting the initial velocity from the final velocity and dividing this by the time it took for the change. Acceleration – a measure of the change in the velocity of an object over a period of time. Assuming he does not speed up or slow down, what is his speed in meters per second? 2. Speed may be defined as distance travelled by the body in unit interval of time. We then went to the computer lab and spent a 2-period block of time working on the Speed and Velocity portion of the Force and Motion. A 300 N force acts on a 25 kg object. To compare and contrast speed and velocity. Angular Momentum – a concept used to describe the spinning momentum of an object. The following data was collected from his workout. Speed, Velocity, and Acceleration Problems Use your OWN PAPER, and show ALL work. Velocity is the measure of. Explore how circular motion relates to the bug's x,y position, velocity, and acceleration using vectors or graphs. 1) How do we KNOW that inertia affects the acceleration of an object? 2) Why is it so important to make sure the balloon was the same size for each test (in the Balloon Rocket lab)? 3) What could have caused the difficulty you experienced in getting the straw to slide down the string smoothly? (more than one thing) 10/21 + 22:. At the top of each graph, select the Σ icon to display the graph's statistics. Acceleration is also a vector. In a lab experiment, a ball is rolled down a ramp so that it leaves the edge of the table with a horizontal velocity v. The average velocity of the cart is will be equal to the instant velocity and the acceleration will be zero since there is no force acting on the cart during its motion on the ideal frictionless track. Lab - Air Resistance Here is a video about air resistance The goal of this lab is to model an object falling with an air resistance force. (1 mark) b. Carefully read the lab and follow along. Quickly find that inspire student learning. USING THE INCLINED PLANE TO MEASURE SPEED AND ACCELERATION. What is the acceleration?. The acceleration graph in Figure 2. With this worksheet, you can make solving speed, velocity, and acceleration problems fun! Students may solve the problem in the work box, and then cut and glue the answer in the correct box. The following practice questions ask you to find the position, velocity, speed, and acceleration of a platypus in …. Read more Newton's Laws. 0 km/s to 1. Angular and Linear Velocity Introduction: In this lesson, the velocity of a particle traveling on a circular path will be examined. Exam 1 Review Questions PHY 2425 - Exam 1. Showing top 8 worksheets in the category - Speed And Velocity With Answer Key. or has a greater change in velocity during the. Predictions for Lab 3. speed and acceleration of an object sliding down the surface? Calculations: The acceleration due to gravity, final velocity. We then went to the computer lab and spent a 2-period block of time working on the Speed and Velocity portion of the Force and Motion. An adjustable slider-crank apparatus and a computer simulation will show you some eﬀects of changing the proportions of the slider-crank mechanism on piston velocity and acceleration. time graphs relate to motion diagrams and position vs time graphs. The centripetal force consists of string tension (up) and gravity (down) so. A body in one dimensional motion has zero speed at an instant. There will be some graphing and conclusion questions near the end, but be sure to work quickly to collect your data first so that you make sure there is enough time to complete the lab. Speed is the absolute value of velocity and velocity is the first derivative of the position function. Experiment I - Kinematics in One Dimension Note A guide for LoggerPro Software is given in Appendix 1 at the end of this lab manual. rate, velocity d. Average and instantaneous acceleration. speed in a certain direction. time, velocity vs. A minus sign means that the car is decelerating. ) Request Teacher Toolkit The Physics in Motion teacher toolkit provides instructions and answer keys for study questions, practice problems, labs for all seven units of study. On the motion task cards I chose to have several situations for my students to differentiate between speed, velocity, and acceleration. Velocity/Acceleration Worksheets. What is the speed of a walking person in m/s if the person travels 1000 m in 20 minutes? 0. a = acceleration, v = change in velocity or speed, and t = time. Acceleration is also a vector. An object accelerates uniformly between for three seconds, and then steadily increases the acceleration for the next three seconds. time graphs. When you tackle calculus problems involving position, velocity, and acceleration, it's important to know how these three vectors relate to each other. Which of the following is a measure of velocity? a. Acceleration means a change in speed and/or direction. Name the force that caused the stone to fall. (Equivalent to American high school diploma) If this is too basic for you, you can try the more advanced version…. Speed and Velocity Converter - Convert speed and velocity units - m/s, km/h, knots, mph and ft/s; Only emails and answers are saved in our archive. State your answer: That means that every second the rocket’s speed increases by _____. The acceleration is the change in velocity ÷ time, which is -8 m/s ÷ 2 s = -4 m/s 2. Uniform Motion: Velocity Velocity vsvs time graphtime graph Uniform Motion: Verbal Description of Motion. Acceleration - a measure of the change in the velocity of an object over a period of time. vector and they solve 4. The difference between scalar and vector quantities is also discussed. Acceleration is the rate of change in the speed of an object. Therefore the velocity is positive and constant. Home About Contact IPC Environmental Systems Anatomy STAAR Help UIL Today in Class Test Review- Answer Key Force & Motion. 9)How long does it take for a car to change its velocity from 5m/s to 60m/s if the acceleration is 5m/s^2? 10) if you are walking at a constant velocity of 20km/h and a car passed you by at the speed of 35km/h from behind, what is the cars velocity from your viewpoint?. This product includes almost everything you will need for this lab with the exception of measuring tape, timing device, and metal washers (or other similar weights). So if we want to change the motion of the. You speed up if the acceleration and velocity point in the same direction. What is the. A ball rolls down a ramp for 15 seconds. Recall that velocity refers to both speed and direction. Let’s start with an example, namely the motion of a ball thrown upward and then acted upon by gravity. This topic covers "Speed, Velocity and Acceleration" of O Level Physics. Suppose you are in a car moving at (initially) 1 m/s. Calculate the acceleration for the following data. In this lab you will learn the difference between speed, velocity, and acceleration. For Most Of The Ride, The Beam Rotates About Its Center In A Horizontal Circle At A Constant Speed. time of a cart rolling down an incline. Speed Velocity Acceleration Worksheet. As an object begins to fall, it moves faster and faster (its velocity increases) due to the acceleration caused by the Earth’s gravity. Time and Acceleration vs. Look at your acceleration for the first test. Describe the motion of your object for procedure one. A place or object used for comparison to determine if another object is in motion is called a. On the other hand, velocity is a vector quantity; it is a direction-aware quantity. What is the acceleration? 7. Average Speed of a Constant Velocity Vehicle Lab. acceleration = velocity time v f = v o + a t final velocity = initial velocity + acceleration time 2 v f 2 = v o 2 + 2 a d (final velocity)2 = (initial velocity) + 2 acceleration distance d = v o t + ½ a t2 distance = initial velocity time+ ½ acceleration time2 This is the only formula with distance d, time t, and acceleration, a. Your goal in this lab is to learn how to describe various kinds of motion in more detail. A dog runs with an initial speed of 7. Creating the velocity vs. Similarly, that's what i did for position and i had the above reasult. group the answers to the following questions. Complete the statements below: A. It is calculated by subtracting the initial velocity from the final velocity and dividing this by the time it took for the change. none of the answers. Explanation:. STUDENT WORKSHEET: Force and Acceleration Exercises. 5 m/s on a waxed floor. Move the little man back and forth with the mouse and plot his motion. To learn about acceleration. Impossible to answer without knowing the initial speed of the ball. No longer can you simply think of acceleration as gaining speed and decelerating as losing speed. Speed, Velocity & Acceleration Problems Directions: Answer each question in your science journal. Acceleration is the derivative of velocity, and velocity is the derivative of position. Your bicycle has a mass of 9. Acceleration – a measure of the change in the velocity of an object over a period of time. Acceleration, rate at which velocity changes with time, in terms of both speed and direction. Sample answer: Acceleration of the toy car was greater on the steeper ramp. Directions: Use this review sheet as GUIDE as to what you need to know. 5 m/s 2 for a time period of 10 s. Adjust the Initial Position and the shape of the Velocity vs. Read and article about Newton's three laws and answer questions. Given the following position curve, sketch the corresponding velocity curve. Speed, Velocity, and Acceleration Goals: To investigate what is needed to describe motion completely. Pre-lab Questions 1. In this acceleration and average speed activity, students learn the equations for acceleration and average speed. A velocity vs. But 3 seconds later, at the bottom of the slope, its speed is 22 m/s. Some objects do both at the same time! The time it takes for an. meters due south in 5. When I let him move at a velocity of 4 meters/sec for two sec. v = final velocity or speed - initial velocity or. In the tutorial on free vibration, a mechanism called the Scotch Yoke was examined in order to explain sinusoidal or harmonic motion. Along which path would you have to move with the greatest speed to arrive at the destination in the same amount of time? 2. v(t) = i + 2t j + 0k = i +2t j. Speed, Velocity and Acceleration Lab Name_____ In this lab, you will compare and learn the differences between speed, velocity, and acceleration. What is the force acting on an object with a mass of 2489 kg and an acceleration of 6. Read each question carefully and select the best answer from the. Similarly, that's what i did for position and i had the above reasult. In this experiment, since the coefficient of kinetic friction is to be measured, constant speed motion of block M requires a zero acceleration. STUDENT WORKSHEET: Force and Acceleration Exercises. For the following quiz, you will need a pencil, scratch paper and a calculator. Angular and Linear Velocity Introduction: In this lesson, the velocity of a particle traveling on a circular path will be examined. Find the spot that marks 20m from the starting line. There is no horizontal acceleration (angular velocity reaches maximum magnitude at bottom, so momentarily does not change). meters due south in 5. final velocity was 7 m/sec, what was the acceleration of the ball ? 0.