Physics 151 Week 2 Day 3 Topics Motion Diagrams & Motion Graphs Motion Definitions Velocity to position

Two Ships Passing in the Night Ships P and Q move with the position graphs shown. Both ships are at the origin at t = 0s. When does one pass the other? at t = 2 s. at t = 1 s and at t = 3 s. at t = 1 s, 2 s, and 3 s. P and Q never pass one another. Answer: A Slide 2-34

Two Ships Passing in the Night Ships P and Q move with the position graphs shown. Both ships are at the origin at t = 0s. When does one pass the other? at t = 1 s and at t = 3 s. Answer: A Slide 2-34

Two Ships Passing in the Night Ships P and Q move with the position graphs shown. Both ships are at the origin at t = 0s. Do P and Q ever have the same velocity? If so, at what time or times? P and Q have the same velocity at 2 s. P and Q have the same velocity at 1 s and 3 s. P and Q have the same velocity at 1 s, 2 s, and 3 s. P and Q never have the same velocity. Answer: A Slide 2-34

Answer Ships P and Q move with the position graphs shown. Both ships are at the origin at t = 0s. Do P and Q ever have the same velocity? If so, at what time or times? P and Q have the same velocity at 2 s. Answer: A Slide 2-35

Motion Diagrams

Representations of Motion Motion diagram (student walking to school) Table of data Graph Slide 2-9

A. B. C. D. Checking Understanding Here is a motion diagram of a car moving along a straight stretch of road: Which of the following velocity-versus-time graphs matches this motion diagram? Answer: C A. B. C. D. Slide 2-13

Answer Here is a motion diagram of a car moving along a straight stretch of road: Which of the following velocity-versus-time graphs matches this motion diagram? Answer: C C. Slide 2-14

A. B. C. D. Checking Understanding A graph of position versus time for a basketball player moving down the court appears like so: Which of the following velocity graphs matches the above position graph? Answer: C A. B. C. D. Slide 2-15

Answer A graph of position versus time for a basketball player moving down the court appears like so: Which of the following velocity graphs matches the above position graph? Answer: C C. Slide 2-16

Can you move? Fill in the tables for these motion events by indicating whether or not a motion event is possible.  If it is, give an example.  If not, explain why not. Displacement Final Position Possible? Example/Explanation Not 0 Average Speed Average Velocity Possible? Example/Explanation Not 0 Answer: B Slide 1-7

There and Back You and a friend decide to drive to Las Vegas, Nevada on Saturday over Labor Day weekend to go to a concert with some friends who live there. You figure you have to reach the vicinity of Las Vegas by 6 PM in order to meet your friends for dinner before the concert. It's 574 miles from UNM to the Las Vegas strip. You'd like to stop for lunch and gas bout noon. What does your average velocity need to be? It's almost all highway driving from here to Las Vegas. If you keep your speed approximately constant, what speed should your speedometer read while you are driving? After you return to UNM, what is your displacement from the time you left to go to Las Vegas? What is the total distance traveled? What is your average speed and velocity? Answer: B Slide 1-7

Where’s the train? A train is moving at a steady 30 m/s. At t = 0, the engine passes a signal light at x = 0. Without using any formulas, find the engine's position at t = 1s, 2s, and 3s. Express your reasoning in words. Slide 2-34

Velocity to Position: Example 1 Find the position at times t = 1, 2, 3, 4, and 5 seconds. Assume x (t = 0 sec) = 0 m. What is the displacement of the object between t = 1s and t = 3 s? Answer: A Slide 2-34

Velocity to Position: Example 2 Describe in words the motion of the object whose velocity graph is given below. What is happening at t = 2 s? Draw a motion diagram of the objects motion. Draw the corresponding position vs. time graph. Assume initial position is 5 m. Give an example of an object that would move this way Answer: A Slide 2-34

Acceleration Acceleration is: The rate of change of velocity The slope of a velocity- versus-time graph Slide 2-20

Reading Quiz If Sam walks 100 m to the right, then 200 m to the left, his net displacement vector points to the right. to the left. has zero length. Cannot tell without more information. Answer: B Slide 1-6

Answer If Sam walks 100 m to the right, then 200 m to the left, his net displacement vector points to the left. Answer: B Slide 1-7

Reading Quiz Velocity vectors point in the same direction as displacement vectors. in the opposite direction as displacement vectors. perpendicular to displacement vectors. in the same direction as acceleration vectors. Velocity is not represented by a vector. Answer: A Slide 1-8

Answer Velocity vectors point in the same direction as displacement vectors. Answer: A Slide 1-9