Download Review Packet for Test on Newton`s Laws, Impulse and Momentum

Review Packet for Test on Newton’s Laws, Impulse and Momentum
Part I
1. An object traveling at 16 m/s enters a frictional area. It comes to rest after a time of 4 s. The
coefficient kinetic of friction of the frictional area is
1. 0.4
2. 0.5
3. 0.9
4. 1.6
2. A ball of mass m is dropped through the air in a gravitational field. The magnitude of the force of
air resistance is bv2 where b is a positive constant. What is the terminal speed of the ball?
1. gm/ √b
2. √(gm/b)
3. √(g/b)
4. √(gm)/b
3. Four forces are acting on an object as shown in the diagram.If
the object is moving with a constant velocity, the magnitude of force
F must be
1. 0 N
2. 20 N
3. 40 N
4. 70 N
4. A book weighing 20. newtons slides at a constant velocity down a ramp inclined at 30.° to the
horizontal as shown in the diagram. What is the force of friction between the
book and the ramp?
1. 10. N up the ramp
2. 17 N up the ramp
3. 10. N down the ramp
4. 17 N down the ramp
5. 20 N up the ramp
5. A rope of negligible mass supports a block that weighs 30 N, as shown. The breaking
strength of the rope is 50 N. The largest acceleration that can be given to the block by pulling
up on it with the rope without breaking the rope is most nearly
(A) 6 m/s2
(B) 6.7 m/s2
(C) 10 m/s2
(D) 15 m/s2
6. A force F is needed to accelerate a series of boxes along a frictionless floor as shown. What is the
tension in rope B?
1. F/3
2. F/2
3. F/5 F
4. 5/6 F
7. An arrow is shot through an apple. If the 0.1 kg arrow changes speed by 10 m/s during the
collision (from 30 m/s to 20 m/s) and the apple goes from rest to a speed of 2 m/s during the collisions,
then the mass of the apple must be
1. 0.2 kg
2. 0.5 kg
3. 0.8 kg
4. 1 kg
8. A person pushes a block of mass M = 6.0kg with a constant
acceleration of 5.0 m/s2 straight up a flat surface inclined 30.0° above
the horizontal. The coefficient of kinetic friction between the block
and the surface is μ = 0.40.
What is the pushing force acting on the block?
(A) 60 N
(B) 21 N
(C) 30 N
(D) 51 N
(E) 81 N
9. A box of mass m is pushed along a horizontal floor with constant velocity v. The coefficient of
kinetic friction between the box and the floor is . How much force is needed to push the box?
1. mg
2. mgv
3. mv
4. zero
10. A 2,400-kilogram car is traveling at a speed of 20. meters per second. Compared to the
magnitude of the force required to stop the car in 12 seconds, the magnitude of the force required to stop
the car in 6.0 seconds is
1. half as great
2. twice as great
3. the same
4. four times as great
11. A ball with a mass of 0.50 kg and a speed of 6 m/s collides perpendicularly with a wall and bounces
off with a speed of 4 m/s in the opposite direction. What is the magnitude of the impulse acting on the
ball?
(A) 1 Ns
(B) 5 Ns
(C) 2 m/s
(D) 10 m/s
A.
B.
C.
D.
12. A tractor-trailer truck is traveling down the road. The mass of the trailer is 4 times the mass of the
tractor. If the tractor accelerates forward, the force that the trailer applies on the tractor is
4 times greater than the force of the tractor on the trailer.
2 times greater than the force of the tractor on the trailer.
equal to the force of the tractor on the trailer.
zero since the tractor is pulling the trailer forward.
13. Assume the objects in the following diagrams have equal mass and the strings holding
them in place are identical. In which case would the string be most likely to break?
14. A push broom of mass m is pushed across a rough horizontal floor
by a force of magnitude T directed at angle θ as shown. The coefficient of
friction between the broom and the floor is μ. The frictional force on the
broom has magnitude
(A) μ(mg + Tsinθ)
(B) μ(mg – Tsinθ)
(C) μ(mg + Tcosθ)
(D) μ(mg – Tcosθ)
15. The cart of mass 10 kg shown above moves without frictional loss on a
level table. A 10 N force pulls on the cart horizontally to the right. At the same
time, a 30 N force at an angle of 60° above the horizontal pulls on the
cart to the left. What is the magnitude of the horizontal acceleration of the
cart?
(A) 0.5 m/s2
(B) 1.6 m/s2
(C) 2.0 m/s2
(D) 2.6 m/s2
16. The diagram below shows a 50-kilogram crate on a rough plane at angle  to the horizontal. The
crate is pushed at constant speed up the incline from point A to point B by force F.
If angle  were increased, what would be the effect on the
magnitude of force F and the magnitude of the frictional force, f,
acting on the box?
(A) F would increase and the magnitude of f would decrease.
(B) F would increase and the magnitude of f would increase.
(C) F would decrease and the magnitude of f would decrease.
(D) F would increase and the magnitude of f would remain the same.
17. A descending elevator of mass 1,000 kg is uniformly decelerated
to rest over a distance of 8 m by a cable in which the tension is 11,000 N.
The speed vi of the elevator at the beginning of the 8 m descent is most
nearly
(A) 4 m/s
(B) 10 m/s
(C) 13 m/s
(D) 16 m/s
18. A 2.0-kilogram body is initially traveling at a velocity of 40. meters per second east. If a constant
force of 10. newtons due west is applied to the body for 5.0 seconds, the final speed of the body is
(A) 15 m/s
(B) 30 m/s
(C) 65 m/s
(D) 130 m/s
19. Two 5 kg masses are attached to opposite ends of a long massless
cord which passes tautly over a massless frictionless pulley. The
upper mass is initially held at rest on a table 50 cm from the pulley.
The coefficient of kinetic friction between this mass and the table is
0.2. When the system is released, its resulting acceleration is closest
to which of the following?
(A) 9.8 m/s2
(B) 7.8 m/s2
(C) 4.9 m/s2
(D) 3.9 m/s2
20. A block of mass 3m can move without friction on a horizontal table.
This block is attached to another block of mass m by a cord that passes over a
frictionless pulley, as shown above. If the masses of the cord and the pulley
are negligible, what is the magnitude of the acceleration of the descending
block?
(A) Zero
(B) g/4
(C) g/3
(D) g
21. A tennis ball of mass m rebounds from a racquet with the same speed v as it had
initially as shown. The magnitude of the momentum change of the ball is
(A) 0
(B) 2mv
(C) 2mv sin
(D) 2mv cos
Review Packet for Test on Newton’s Laws, Impulse and Momentum
Part II
1. A 20.0-kilogram monkey hangs initially at rest from two
vines, A and B. as shown. Each of the vines has length 10 meters
and negligible mass.
a.
On the figure below, draw and label all of the forces
acting on the monkey. (Do not resolve the forces into
components, but do indicate their directions.)
b.
Determine the tension in vine A while the monkey is at rest.
2. A bicyclist is coasting along a straight, horizontal road at a velocity of 8.2 m/s westward. The
bicyclist and his bicycle have a combined mass of 85 kg. The bicyclist applies the brakes with a force of
600 newtons to slow down.
[a] Draw a freebody diagram showing all forces acting on the bicycle while it is being braked.
Label the forces.
[b] Determine the magnitude of the acceleration of the bike caused by the brake. Show equation
and substitution with units.
[c] How long will it take the bike to stop?
3. A helicopter holding a 70-kilogram package suspended from a rope 5.0 meters long
accelerates upward at a rate of 5.2 m/s2.
a. On the diagram, draw and label all of the forces acting on the package.
Neglect air resistance on the package.
b. Determine the tension in the rope.
4. A model rocket of mass 0.50
kg is launched vertically with an
engine that is ignited at time t =
0, as shown above. The engine
provides an impulse of 30.0 N•s
by firing for 2.0 s. Upon reaching
its maximum height, the rocket
deploys a parachute, and then
descends vertically to the ground.
(a) On the figures below,
draw and label a free-body
diagram for the rocket during each of the following intervals.
(b) Determine the magnitude of the average acceleration of the rocket during the 2 s firing of the
engine.
(c) What maximum height will the rocket reach?
(d) At what time after t = 0 will the maximum height be reached?
5.
6.
7.
8. A 0.25 kg ball is thrown vertically upward with an initial speed of 30 m/s. The acceleration due
to gravity can be approximated to 10 m/s2 and the effects of air resistance is NOT neglected. The graph
shows the velocity of the ball on the upward part of its journey.
a. Draw a freebody diagram that shows the forces acting on the ball after it is thrown upward.
b. Estimate the maximum height reached by the ball.
c. At 1.0 seconds,
(i)
determine the acceleration of the ball
(ii)
determine the force of air resistance acting on the ball
d. Use the graph to explain, without any further calculations, that the force of air resistance is
decreasing as the ball moves upward.
e.
Will the ball return back to the ground at 30 m/s? Explain why or why not.
9. A student stands on a scale in an elevator and records the scale reading as a function of time. The data
are shown in the graph below. At time t = 0, the elevator is at rest on the ground floor. Assume that the
positive directions for displacement, velocity, and acceleration are upward.
a.
What is the weight of the student?
b.
On the diagram to the right,
draw and label all of the forces on the student at t = 8 seconds.
c.
Plot the acceleration as a function of time on the following graph.
d.
Write a description of the elevator’s motion over the 20 second interval. Be sure to include
references to speed of the elevator and the direction that the elevator is traveling.