Physics 122 Problems: Describing Motion: Velocity

1. Sketch time-position graphs to describe the following motions.

a) an object starting from the reference point moves eastward for a while at a constant, medium speed

b) from the reference point at a fast westward speed

c) from the reference point at a slow eastward speed

d) an object starting from the reference point moves eastward for a while at a constant, medium speed but then pivots and heads back quickly to the reference point

e) an object starting from the reference point moves westward for a while at a constant rapid speed but then pivots and heads slowly back to the reference point but stops a bit short

f) an object starting from a point somewhat eastward of the reference point moves more to the east for a while at a constant rapid speed but then pivots and heads quickly back to the reference point but stops a bit short.

g) a tennis ball impacting and rebounding from a backboard.

2. Sketch time-position graphs to describe the following motions.

a) an object starting from the reference point accelerates as it moves westward for a while

b) an object starting from the reference point accelerates as it moves eastward for a while

c) an object starting from the reference point decelerates as it moves eastward for a while

d) an object starting from the reference point decelerates as it moves westward for a while.

3. a) What is the primary use of a t-p graph?

b) What secondary information about an object's motion can we get from the t-p graph?

c) How do we get this secondary information from the t-p graph?

4. a) What is the primary use of a t-v graph?

b) What secondary information about an object's motion can we get from the t-v graph?

c) How do we get this secondary information from the t-v graph?

5. Change these

t-p graphs into

the equivalent

t-v graphs.

6. What is the distinction between a scalar and a vector?

7. Which value is speed? velocity? i) 6.3 m/s ii) 0.48 m/s, 45⁰.

8. a) Define: reference point.

b) Define: frame of reference.

9. a) What determines if an object's position is negative?

b) What type of motion creates a negative displacement?

10. Create a small map of the following motion. An aardvark exits its den and waddles at 0.07 m/s to a spot 4.5 m 90⁰. (How long would this take?) Then it waddles along 270⁰ for 10 minutes. (Hint: How far W does it move in the 10 min?)

11. A humming bird is located 5 m, 90⁰ from its nest. A second humming bird hovers at a feeder on a pole located 7.5 m, 270⁰, from the same nest.

a) What is the position of the first humming bird?

b) And the position of the second humming bird?

c) What is the distance of the two birds from each other?

12. An elephant sauntering across a grassland is seen 25 m E from a watering hole at one time and 127.5 m W from it at a later time.

a) What is its displacement from the first to the second spot?

b) Displacement is similar to what previous term?

13. Sketch a t-p story graph for this situation: object starts from reference point and moves 12 m E in 20 s, pauses for 5 s, moves another 15 m E in 20 s, pauses for 10 s and then, in 25 s, moves back toward the reference but stops 2 m short.

14. Find the average velocity (in m/s) of an object that:

a) moves 50 m in 37 s.

b) moves from a spot 3 m E to a spot 55 m E in 1.4 minutes.

c) moves eastward 0.6 km from a spot 5 m E in 0.4 hr. (By the way, where does the object end up?)

d) moves from a spot 20 m E to a spot 80 m W in 2.3 minutes.

e) moves from a spot 200 m E of the reference point to a spot just 10 m E of it in 0.25 hr.

15. a) At 10:05, a meteor is located 10 000 km out. By 10:06 it is 70 km out. Find its average velocity.

b) Where would it have been at 10:00?

16.Find a cat's average velocity as it retreats 85 m from a rat, foaming at the mouth, in 6 s.

17. If a volley ball has an average velocity of 8.5 m/s, it will fly how far in 0.9 s?

18. If the average velocity of a snail is 2 * 10 ^{- 3} m/s, in how many seconds will it move 5 cm?

19. a) Use this data to plot a t-p graph.

Time (s): 1 2 3 4 5 6 7 8

Distance (m): 4 8 12 16 20 24 28 32

b) Find the slope.

20. a) Plot a time-position graph from the following data.

x(time, s) 0 3 5 7 9 11 13 15 17

y(position, m) 0 6 11 15 18 20 21 21.5 21.1

b) Find the instantaneous velocities (tangent slopes) at 4 and 8 s.

21. A field hockey player running toward the goal at 0.9 m/s shoots the ball ahead at 2.3 m/s. At what times do the player and ball reach the net 20 m ahead?

22. A bird flying at 4.3 m/s is 20 m from its nest when it spits out a distasteful bug at 0.2 m/s. At what times do the bird and bug arrive at the nest?

23. A person stands on a white line on a moving sidewalk gliding along at 2.2 m/s. When the person is 200 m from the end of the moving sidewalk, they start walking backwards at 0.6 m/s.

a) When will the white line reach the end?

b) When will the person reach the end?

24. Richard versus the killer squirrel: the squirrel gives Richard, running at 1.4 m/s, a five minute head start. If the furry rabid critter runs at 2.1 m/s, at what time and distance will it overtake and bring down its human prey.

25. Amy and the killer bees: Amy hoses down a nest of killer bees and starts to run away at 1.3 m/s. Six minutes later a soggy bee emerges and, spotting motion ahead, flies off in pursuit at 4.2 m/s. How long and how far away does it get revenge?

26. Fido and the frisbee: Fido's owner tosses a brand new 25 $ "Olympic gold" model frisbee at 4.6 m/s. Ten seconds later, the fleabag clues in and starts running after it at 4.9 m/s. When and where will the mut catch and chew the frisbee into small, shiny, expensive pieces?

27. A snail moves for 7 min at 0.02m/s before a frog starts to trail it at 0.16 m/s. At what time and distance do they meet for lunch?