Newton’s Laws Packet
Pre AP Physics
1. What acceleration will result when a 12 N net force to the right is applied to a 3 kg object
resting on a surface?
b. What acceleration will result when the same net force is applied to a 6 kg object?
2. A horizontal net force of 16 N causes a crate to accelerate at the rate of 5.0 m/s2. Determine
the mass of the crate.
3. An object is accelerating at 2 m/s2. If the net force is tripled, and the mass remains the same,
what is the new acceleration?
b. If the acceleration is still 2 m/s2, the mass is doubled and the net force remains the same,
what is the new acceleration?
c. If the acceleration is still 2 m/s2, the mass is tripled and the net force is doubled, what is
the new acceleration?
4. Write an expression for the value of FN in each situation below.
Fpush
Fpull
m
m
m
5. Using the diagram below, list at least 5 action-reaction pairs.
6. A 15 kg object is being pulled upward by a massless rope with an acceleration of 3.0 m/s2.
What is the tension in the rope? [192 N]
b. The object is now accelerating downward at 3.0 m/s2. What is the tension in the rope? [102 N]
7. A 10 kg mass rests on a horizontal surface. The frictional force opposing the motion is 20 N.
If a 100 N force is applied to the object, what will its acceleration be? [8.0 m/s2]
8. A man stands in an elevator that accelerates up. His mass is 50 kg. The scale reads the man
is 600 N. What is the actual weight of the man? What is his acceleration? [490 N, 2.2 m/s2]
9. A 100 N box is accelerated across the floor to the left with an applied force of 20 N. The
object encounters 10 N of friction. Determine the normal force, the net force, the coefficient of
friction (µ) between the object and the surface, the mass and the acceleration of the object. [Fnet
= 10 N; FN = 100 N; m = 10.204 kg; a = 0.98 m/s2; µ = 0.10]
10. An object is accelerating at 2 m/s2. If the net force is tripled and the mass of the object is
halved, what is the new acceleration?
11. FBD for four situations are shown below. The net force is known for each situation. Write the
horizontal and vertical net force equations, then solve for the unknown values.
Fnet = 0 N
C
B
Fnet = 900 N, up
m
A
50 N
m
Fnet = 60 N
left
80 N
200 N
200 N
300 N
F
Fnet = 30 N
right
m
D
10 kg
20 N
E
G
H
12. Select the correct law for the given application.
a. The driver loaded his truck with grain and it could not accelerate as rapidly.
b. Anne steps from the boat to the dock and is surprised to see the boat move in the
opposite direction.
c. Anne and Jim stand on skateboards. Anne has a rope tied around her waist and her
hands up in the air. Jim pulls on the rope and they both move towards each other.
d. The coffee on the dash slid to the side when the driver made a turn.
e. The book on the floor of the bus slid to the front as the driver applied the brakes.
f. The driver drove his friend’s Mustang which had a smaller engine and discovered it
drove sluggishly.
g. The student was whirling a rubber stopper on the end of the string when the string broke
and the stopper went along a tangent to the circle and hit the wall.
h. It took longer for the elevator to reach the top floor when it had more people on it.
i. When the gun was fired, it pushed on the shoulder of the man.
13. A boy and his skateboard have a combined mass of 80 kg. If he is traveling 6 m/s, what net
force is needed to stop him in 4 seconds? [-120 N]
14. An applied force of 50 N is used to accelerate an 8.164 kg object to the right across a
frictional surface. The object encounters 10 N of friction. Determine the normal force, the net
force and the acceleration of the object. [FN = 80 N; Fnet = 40 N; a = 4.9 m/s2]
15. After initially picking the stone up off the ground, a man exerts a 148 N force upwards on a
10 kg stone. What is the acceleration of the stone? [5 m/s2]
16. A man who weighs 900 N stands in an elevator on a scale and it reads 1000 N. What
direction is the elevator accelerating and what is the acceleration of the elevator?
[1.089 m/s2 upwards]
17. A man who has a mass of 50 kg stands in an elevator that is accelerating up at 3 m/s2. How
much does this man weigh? What does he read on the scale as he accelerates up? [FW = 490
N, scale = FN = 640 N]
18. A 5 kg object is sliding to the right and is encountering a friction force which slows it down.
The coefficient of friction (µ) between the object and the surface is 0.1. Determine the force of
gravity, the normal force, the force of friction, the net force and the acceleration. [Fnet = -4.90 N;
FN = 49 N; Fg = 49 N; a = -0.98 m/s2; FFR = 4.90 N]
19. A rightward force is applied to a 6 kg object to move it across a rough surface at constant
velocity. The object encounters 15 N of frictional force. Determine the force of gravity, the
normal force, the net force and the applied force. [Fnet = 0 N; FN = 58.8 N; Fg = 58.8 N; Fa = 15
N]
20. A .22 caliber slug moving at 360 m/s hits and embeds in a block of wood to a depth of 0.1
m. If the slug has a mass of 1.8 g:
a. How long does it take the slug to stop? [5.56 x 10-4s]
b. What is the average retarding force? (What force causes the bullet to stop?) [-1166.4 N]
21. A 20 kg sled rests on a horizontal surface. If it takes 75 N to start the sled in motion and 60
N to keep it moving at a constant speed, what are the coefficients of static and kinetic friction
respectively? [µs = 0.383; µk = 0.306]
22. A leftward force is applied to a 5 kg object to move it across a rough surface with a leftward
acceleration of 2 m/s2. The coefficient of friction, µ, between the object and the surface is 0.1.
Determine the gravitational force, the normal force, the applied force, the frictional force and the
net force. [Fnet = 10 N; FN = 49 N; Fg = 49 N; Fa = 14.9 N; FFR = 4.9 N]
23. A rightward force of 25 N is applied to a 4 kg object to move it across a rough surface with a
rightward acceleration of 2.5 m/s2. Determine the gravitational force, the normal force, the
frictional force, and the coefficient of friction between the object and the surface. [FFR = 15 N; FN
= 39.2 N; Fg = 39.2 N; µ = 0.383]
24. An 8.0 kg rocket is fired and encounters a force of air resistance of 4.9 N. If the rocket’s
engines applied 100 N of thrust:
a. What is the net force on the rocket? [16.7 N]
b. What is the rocket’s acceleration? [2.09 m/s2]
25. A 1 kg object can be accelerated at 10 m/s2. If you apply this same force to a 4 kg object,
what will its acceleration be? [2.5 m/s2]
26. A 15 kg cart is pushed on a frictionless surface from rest horizontally by a 30 N force.
a. What is the cart’s acceleration? [2 m/s2]
b. How far will it travel in 10 seconds? [100 m]
c. What is its velocity at the end of 10 seconds? [20 m/s]
27. The coefficient of static friction between a 100 kg box and a surface is 0.30. What is the
maximum force that can be applied to the box horizontally before it will move? [294 N]
28. A 90 N box rests on a horizontal surface. If a force of 45 N is applied to the box, will it move
if the coefficient of static friction is 0.773? [no; FFR = 69.57 N]
29. How much force must be applied by a worker to slide a 250 N refrigerator across the floor at
a constant speed if the coefficient of sliding friction is 0.226? [56.5 N]
30. Lemon and her friends are going for a ride. If their combined weight is 7.5 N and it takes 3.4
N of force to get them going, what is the coefficient of static friction between the ground and
their box sled? [µ = 0.453]
b. How much force would be needed to keep Lemon and her friends sliding at a constant speed
if the coefficient of sliding friction is 0.230? [1.725 N]
31. A 2 kg crate with initial speed of 3 m/s slides 2 m to a stop.
a. What is the coefficient of kinetic friction? [0.230]
b. What force would be needed to keep the crate moving at a constant speed? [4.508 N]
32. A force of 300 N is sufficient to keep a 1000 N wood crate moving at a constant velocity
across a wooden floor. What is the coefficient of kinetic friction (µk)? [µk = 0.300]
33. A 1000 kg truck going 75 km/h slides 70 m to a stop. Find the coefficient of kinetic friction
(µk). [µk = 0.316]
34. A force of 1000 N is applied to a 10,000 N car. If the µk is 0.04, what is the car’s
acceleration? [0.588 m/s2]
35. The coefficient of kinetic friction between a rubber tire and the road is 0.5.
a. Find the minimum time in which a 1500 kg car whose initial velocity is 26.8 m/s will stop.
[5.469 sec]
b. What distance will the car cover in this amount of time? [73.290 m]
36. A bowling ball with an initial velocity of 3 m/s rolls along a level floor for 50 m before coming
to a stop. What is the µk between the ball and the floor? [µk = 0.0092]
37. A tractor accelerates a 900 kg log to 15 m/s in 30 s. What was the net force? [450 N]
b. If the coefficient of friction is 0.4, what was the friction force applied? [3528 N]
c. What was the force of the tractor? [3978 N]