333 PHYSICS – UNIT 1 REVIEW NAME: ANSWERS
LINEAR MOTION
1. How can you be both at rest and also moving about 107,000 km/h at the same time?
Relative to different places you can have different answers
2. You cover 10 meters in a time of 1 second. Is your speed the same if you cover 20 meters in 2 seconds? Explain.
Same speed for same ratio
3. Does the speedometer of a car read instantaneous speed or average speed? Why?
Instantaneous, 1 pt in time
4. Which quantity, speed or velocity, does NOT depend of direction? Defend your answer.
Speed is just how fast
5. What two controls on a car cause a change in speed? What control causes a non-speed change in velocity?
Gas pedal and brake. Steering wheel.
6. What is the acceleration of a car moving along a straight-line path that increases its
speed from zero to 100 km/h in 10 s?
10km/h / s
7. By how much does the speed of a vehicle moving in a straight line change each second when it is accelerating at 2 km/h/s? At 4 km/h/s? At 10 km/h/s?
2km/h, 4km/h, 10km/h
8. What is the meaning of free fall ?
No air and gravity only force
9. For a freely falling object dropped from rest, what is the instantaneous speed at the
end of the fifth second of fall? The sixth second?
50m/s, 60m/s
10. For a freely falling object dropped from rest, what is the acceleration at the end of the fifth second of fall? The sixth second? At the end of any elapsed time t ?
10m/s2
11. How far will a freely falling object fall from rest in five seconds? Six seconds?
125m, 180m
12. How far will an object move in one second if its average speed is 5 m/s?
5m
13. How far will a freely falling object have fallen from a position of rest when its
instantaneous speed is 10 m/s?
after 1sec it will have fallen 5m
14. Does air resistance increase or decrease the acceleration of a falling object?
Decrease acceleration
15. Jake runs along a train flatcar that moves at the velocities shown at right. Calculate the relative velocities of Jake as seen by an observer on the ground for each situation. (To the right = +, to the left = -)
A = 4m/s to right B= 4m/s to the left
C = 10m/s to right D = 12m/s to right
16. Below you see before and after snapshots of a car’s velocity. The time interval between
before and after for each is the same.
a. Rank the cars in terms of the change in velocity (absolute value).
A = 10m/s to right B= 10m/s to right
C = -5m/s(slow down) D = 0m/s
b. Rank them in terms of acceleration, from greatest to least (absolute value).
A and B > C > D
17. Calculate your average walking speed when you step 1 meter in 0.5 second.
2m/s
18. Calculate the speed of a bowling ball that moves 8 meters in 4 seconds.
2m/s
19. Calculate the distance (in km) you run if you maintain an average speed of 8 km/h for 1 hour.
D = vt = 8km
20. These are drawings of same-size balls of different weights thrown straight downward. The speeds shown occur immediately after leaving the thrower’s hand. Ignore air resistance. Rank their accelerations from greatest to least.
All the same, doesn’t matter how fast you throw them. After you let go, all are in free fall a=g
21. Calculate the distance you will travel if you maintain an average speed of 10 m/s for 40s.
400m
22. Calculate the acceleration of a car (in km/h/s) that can go from rest to 100 km/h in 10 s.
10km/h / s
23. Calculate the acceleration of a bus that goes from 10 km/h to a speed of 50 km/h in 10s.
4km/h / s
24. Calculate the acceleration of a ball that starts from rest and rolls down a ramp and gains a speed of 25 m/s in 5 seconds.
5m/s2
25. Calculate the instantaneous speed (in m/s) at the 10-second mark for a car that accelerates
at 2 m/s2 from a position of rest.
2m/s
26. Calculate the speed (in m/s) of a skateboarder who accelerates from rest for 3 seconds down a ramp at an acceleration of 5 m/s2.
15m/s
27. Calculate the instantaneous speed of an apple 8 seconds after being dropped from rest.
80m/s
28. A sky diver steps from a high-flying helicopter. If there were no air resistance, how fast would she be falling at the end of a 12-second jump?
120m/s
29. Calculate the vertical distance an object dropped from rest would cover in 12 seconds if it
fell freely without air resistance.
D = ½ gt2 = 720m
30. If a freely falling rock were equipped with a speedometer, by how much would its
speed readings increase with each second of fall?
10m/s
31. Which has more acceleration when moving in a straight line—a car increasing its speed from 50 to 60 km/h, or a bicycle that goes from zero to 10 km/h in the same time? Defend your answer.
Same….same change over same time
32. Correct your friend who says, “The dragster rounded the curve at a constant velocity of 100 km/h.”
Changing direction does NOT equal constant velocity
33. What is the acceleration of a car that moves at a steady velocity of 100 km/h due
north for 100 seconds? Explain your answer
zero. No change in speed or direction
34. Tiffany stands at the edge of a cliff and throws a ball straight up at a certain speed
and another ball straight down with the same initial speed. Neglect air resistance.
a. Which ball is in the air for the longest time?
Ball thrown upwards
b. Which ball has the greater speed when it strikes the ground below?
Same! Ball thrown upwards will come back down with same speed that the other ball was thrown at and then continue on in same fashion.
35. A ball is thrown straight up.
a) What will be the instantaneous velocity at the top of its path?
zero
b) What will be its acceleration at the top?
10m/s2
c) What is the acceleration on the way to the top?
10m/s2
d) What is the acceleration on the way down from the top?
10m/s2
36. If you throw a ball straight upward at a speed of 10 m/s,
a) how long will it take to reach zero speed?
1 second
b) How long will it take to return to its starting point?
2 second
c) How fast will it be going when it returns to its starting point?
10m/s downward
37. Calculate the hang time of an athlete who jumps a vertical distance of 0.75 meter.
Think of it in reverse. How long does it take to fall 0.75m? g = 10m/s2
D = ½ gt2 t = 0.387s to fall down. Multiply by 2 to include time on way up. 0.774s
38. Describe the motion made by the object that created the spark tape below.
Slowing down…moving at slow constant speed, speeding up
39. A boy shoots a toy arrow straight up as shown at 40m/s.
a) How long does it take to reach peak? 4sec
b) How high does it go to reach the peak? 80m
c) How high is it above boy after 5 seconds? 75m, after 4sec, it will fall 5m from peak from 4-5s
d) what is the total distance it travels after 8seconds. 160m