Download Semester 1 Concept Questions

Subterm 1 Review Questions
(Motion in One & Two Dimensions, Newton’s Laws, Energy & Momentum, Circular Motion)
For the final, you may use a 8.5”x11” page of notes. This page must be unique, HANDWRITTEN & one-sided.
Motion in One & Two Dimensions:
1. A car accelerates from 13 m/s to 25 m/s in 6.0 sec
a. What was its acceleration? (2.0m/s2)
b. How far did it travel in this time? (114m)
2. What is the equation for constant velocity motion?
Velocity=change in position/change in time
3. In what way is a projectile (a ball thrown at 30o, for example) using constant velocity motion.
Horizontal component is constant v
4. In what way is a projectile accelerating?
In the y direction
5. A ball is thrown straight upwards. What is the velocity of the ball at the very top of it’s path? What is the
acceleration of the ball at the very top of it’s path?
0 m/s, -9.8 m/s2
6. Three balls are launched from the top of a tall building. One is thrown downward with some velocity V.
Another is thrown upwards with the same velocity V, and the last is dropped.
a. Which hits the ground first? Why? The one thrown down.
b. Which has the greatest acceleration? Why? Same acceleration; gravity
c. Which will have the smallest landing (final) velocity? Why? Same; gravity
7. A penny is dropped from the top of the Empire State Building (380 m tall).
a. How long will it take the penny to reach the ground? (ignoring air resistance) (8.8sec)
b. How fast is the penny going right before it hits the ground? (Ignore air) (-86 m/s)
8. A rock is thrown upward at 5 m/s at an angle of 25o. As it rises, what happens to the horizontal velocity of
the rock? The vertical velocity?
Horizontal stays the same; vertical decreases, stops, then increases.
9. The pilot of an airplane traveling 180 km/h wants to drop supplies to flood victims isolated on an island
160 m below the plane. The supplies should be dropped how many seconds before the plane is overhead?
(5.7 sec)
10. A rocket with a muzzle velocity of 30.0 m/s is launched at a 30.o angle.
a. How long is the rocket in the air?
b. How far down range does the rocket travel? (90.5m)
11. Draw a position vs time graph, velocity vs time graph, & motion map for an object that starts at 3 m, then
returns to the origin in 3 seconds traveling at a constant velocity, then stops for 2 seconds, then turns
around and travels to 10 m in 4 seconds traveling while accelerating.
Newton’s Laws:
12. What is Newton’s 1st Law? Give an example.
13. What is Newton’s 2nd Law? Give an example.
14. What is Newton’s 3rd Law? Give an example.
0N
15. How much force is required to keep 3.0 kg object moving at a constant velocity on a frictionless, airless,
surface?
16. Bart is taking the elevator from the first floor up to the roof. At first Bart feels heavier than he usually is,
then he feels his normal weight, and then he feels lighter than he usually is. How do Newton’s laws explain
this phenomenon?
F=ma; Elevator is accelerating up = heavier feeling; downward acceleration = lighter feeling
17. If an object is at rest, can it be conclude that it has no forces acting on it? Explain.
False, gravity is always acting.
18. A small sports car collides head on with a massive truck.
a. Which vehicle will experience the greatest magnitude force: the car, the truck, or neither? Explain.
Same; equal and opposite
b. Which will undergo the greater magnitude acceleration?
Car because it’s less massive; F=ma
19. What action reaction pair is responsible for pushing a car forward?
Tires and ground
20. Helpful Henry’s car is pushing Flat-tire Fred’s car to the car shop. While the cars are accelerating up to 15
miles/hour Helpful Henry needs to push Fred’s car with 60 N of force. With what force does Flat-tire Fred’s
car push on Helpful Henry’s car?
60 N
21. An 80.0 N sled is pulled at a constant velocity across a horizontal snow surface. A force of 55 N is being
applied to the sled rope at an angle of 35 above the ground.
c. What is the normal force on the sled? (48.5 N)
d. What is the coefficient of kinetic friction between the sled and the snow? (0.929)
22. A car with a weight of 3000. N is accelerated across a level surface at 8.5 m/s2. What is the net force acting
on the car? (be careful here) (2600 N)
Work, Energy & Momentum
23. A worker pulls a 40.0-kg crate with a rope at the 30.0o angle to the horizontal using a 55.0 N force. He
moves the crate a distance of 7.00 m while a frictional force of 35.0 N acts on the crate.
a. How much work does the worker do on the crate?
b. How much for does friction do on the crate? (-245 J)
c. How much work does gravity do on the crate?
d. How much work does the normal force do on the crate?
e. Why is zero work done by gravity & the normal force?
24. A spring, sitting on top of a 2.0 m high counter, has a spring constant of 450 N/m. A 5.5 kg block is held at
rest against the spring, compressing the spring 0.22 m. If the block is then let go, what is the block’s final
velocity right before it hits the floor? (6.6 m/s)
25. A 40. kg boy & his older brother are on top of a 5.0 m tall slide when the younger boy slides down. What is
the boy’s velocity at the bottom of the slide? What if the boy was measured to be going only 6 m/s at the
bottom of the slide. Explain how this could be possible. What is the boy was measured to be going 12 m/s at
the bottom of the slide. Explain how this could be possible.
Work lost to friction
26. A physics teacher hangs a bowling-ball pendulum from the ceiling. He lifts the ball back until it is at face
level and lets go. If the teacher doesn’t lean forward, the ball won’t swing back and hit him in the face. Why
not?
Conservation of Energy
27. A smart car travels down the road at a constant velocity towards a Mini Cooper. If the cars have the same
mass and the same velocity, what is their total momentum when they are traveling towards each other?
What will be their final momentum if the cars crash and become an entangled metal-plastic mass?
0 because they are equal and opposite momentums so one is negative.
28. A 30.0 kg girl who is running at 3.0 m/s jumps on a stationary 10.0 kg sled on a frozen lake. How fast does
the sled move with the girl on it? (2.3 m/s)
29. An astronaut of mass 80. kg caries an empty oxygen tank of mass 10. Kg. He throws the tank away from
himself with a speed of 2.0 m/s. With what speed does he start to move off into space?
30. Gun ammunition is put into an oven and the oven is then turned on. If the bullet is in a gun, the bullet
becomes dangerous. However, if the bullet is by itself, it is the light metal casing that is more dangerous.
Why?
The casing will fly faster and farther causing more damage.
31. If jumping from a 20 foot high building, it is better to land on a mattress a foot thick than a pile of wood one
foot thick? Use the Impulse-Momentum Theory to explain why.
More time = less force
32. A 0.500-kg bullet traveling at 300. m/s hits a 5.0 kg block of wood and becomes imbedded in the block.
a. That is the velocity of the bullet-block combo?
b. The block then slides without friction into a spring. If the spring is compressed .25 m, calculate its
spring constant. (65,000 N/m)
33. A box is sliding across a frictionless surface when a cat falls vertically into it. What happens to the
horizontal velocity of the box?
It decreases because mass increases