m1
m2
37o 37o
m2m
m
3mF
Newton’s Laws of MotionProblems MC Questions
Starting from rest, a 4.0-kg body reaches a speed of 8.0 m/s
in 2.0 s. What is the net force acting on the body?
(A) 16 N
(B) 8.0 N
(C) 4.0 N
(D) 32 N
01
maF
tΔvΔ
a
(A) 250 kg
(B) 24.5 kg
(C) 25.5 kg
(D) 2,450 kg
What is the mass of an object that weighs 250 N on the
surface of the Earth where the acceleration due to gravity
is 9.80 m/s2?
02
mgW
A stack of books rests on a level frictionless surface.
A force F acts on the stack, and it accelerates at 3.0 m/s2.
A 1.0 kg book is then added to the stack. The same force
is applied, and now the stack accelerates at 2.0 m/s2.
What was the mass of the original stack?
(A) 1.0 kg
(B) 2.0 kg
(C) 3.0 kg
(D) 4.0 kg
03
maF
A person of weight 480 N stands on a scale in an
elevator. What will the scale be reading when the
elevator is accelerating downward at 4.00 m/s2?
(A) 284 N
(B) 196 N
(C) 676 N
(D) 480 N
04
maF
mgW
A person on a scale rides in an elevator. If the mass of the
person is 60.0 kg and the elevator accelerates downward
with an acceleration of 4.90 m/s2, what is the reading on
the scale?
(A) 147 N
(B) 294 N
(C) 588 N
(D) 882 N
05
maF
A person on a scale rides in an elevator. If the mass of the
person is 60.0 kg and the elevator accelerates upward with an
acceleration of 4.90 m/s2, what is the reading on the scale?
(A) 147 N
(B) 294 N
(C) 588 N
(D) 882 N
06
maF
An object of mass 6000 kg rests on the flatbed of a truck.
It is held in place by metal brackets that can exert a
maximum horizontal force of 9000 N. When the truck is
traveling 15 m/s, what is the minimum stopping distance if
the load is not to slide forward into the cab?
(A) 15 m
(B) 30 m
(C) 75 m
(D) 150 m
07
maF
ax2vv 2o
2
In the Atwood machine shown in the
diagram, if m1 = 0.40 kg and m2 = 0.60 kg,
what is the magnitude of the acceleration of
the system? (Ignore friction and the mass
of the pulley.) (A) 5.3 m/s2
(B) 3.9 m/s2
(C) 0.98 m/s2
(D) 2.0 m/s2
m1
m2
08
maF
A 10-kg box sitting on a horizontal surface is pulled by
a 5.0-N force. A 3.0-N friction force retards the motion.
What is the acceleration of the object?
(A) 0.20 m/s2
(B) 0.30 m/s2
(C) 0.50 m/s2
(D) 5.0 m/s2
09
maF
In the Atwood machine shown in the
diagram, if m1 = 0.40 kg and m2 = 0.60 kg,
what is the tension in the string? (Ignore
friction and the mass of the pulley.)
(A) 3.1 N
(B) 4.7 N
(C) 7.1 N
(D) 7.5 N
m1
m2
10
maF
A student pulls a box of books on a smooth horizontal floor
with a force of 100 N in a direction of 37° above the
horizontal. If the mass of the box and the books is 40.0 kg,
what is the acceleration of the box?
(A) 1.5 m/s2
(B) 1.9 m/s2
(C) 2.0 m/s2
(D) 3.3 m/s2
11
maF
A traffic light of weight 100 N is supported by two
ropes as shown in the diagram. What are the tensions
in the ropes?
(A) 50 N
(B) 63 N
(C) 66 N
(D) 83 N
37o 37o
12
0F
Two boxes of masses m and 2m are in contact with
each other on a frictionless surface. A force F is
applied to the smaller block as shown in the diagram.
What is the acceleration of the more massive box?
(A) F/m
(B) F/(2m)
(C) F/(3m)
(D) F/(4m)
m2mF
13
maF
An object slides on a level surface in the +x
direction. It slows and comes to a stop with a
constant acceleration of 2.45 m/s2. What is the
coefficient of kinetic friction between the object and
the floor? (A) 0.25
(B) 0.50
(C) 4.9
(D) 1.0
14
Nμf kk
maF
During a hockey game, a puck is given an initial speed of 10 m/s.
It slides 50 m on the ice before it stops. What is the coefficient
of kinetic friction between the puck and the ice?
(A) 0.090
(B) 0.10
(C) 0.11
(D) 0.12
15
Nμf kk
ax2vv 2o
2
maF
During the investigation of a traffic accident, police find
skid marks 90.0 m long. They determine the coefficient of
friction between the car's tires and the roadway to be 0.500
for the prevailing conditions. Estimate the speed of the car
when the brakes were applied.
(A) 9.49 m/s
(B) 21.0 m/s
(C) 42.0 m/s
(D) 29.7 m/s
16
Nμf kk
ax2vv 2o
2
maF
Boxes of masses m and 3m are pulled to the right by a
constant force F as shown in the diagram. The surface
between the more massive box and the horizontal surface is
smooth and the surface between the boxes is rough. If the
less massive box does not slide on the more massive box, what
is the static friction force acting on the less massive box?
(A) F
(B) F/2
(C) F/4
(D) F/3
m
3mF
17
maF
A 10-kg mass slides down a flat hill that makes an
angle of 10° with the horizontal. If friction is
negligible, what is the resultant force on the sled?
(A) 1.7 N
(B) 17 N
(C) 97 N
(D) 98 N
18
Vector Addition
An object with a mass m slides down a rough 37° inclined
plane where the coefficient of kinetic friction is 0.20. What
is the acceleration of the object?
(A) 4.3 m/s2
(B) 5.9 m/s2
(C) 6.6 m/s2
(D) 7.8 m/s2
19
Nμf kk
maF
An object is placed on an inclined plane. The angle of
incline is gradually increased until the object begins to slide.
The angle at which this occurs is θ. What is the coefficient
of static friction between the object and the plane?
(A) sin θ
(B) cos θ
(C) 1/tan θ
(D) tan θ
20
Nμf kk
maF
01
vΔvΔ
mFnet
s 0.2m/s 0.8
kg 0.4Fnet N 16
Starting from rest, a 4.0-kg body reaches a speed of 8.0 m/s
in 2.0 s. What is the net force acting on the body?
maF
Newton’s 2 nd Law
tΔvΔ
a
Kinematics
What is the mass of an object that weighs 250 N on the
surface of the Earth where the acceleration due to gravity
is 9.80 m/s2?
02
gW
m 2m/s 9.8
N 250 kg 5.52
mgW
Weight
A stack of books rests on a level frictionless surface.
A force F acts on the stack, and it accelerates at 3.0 m/s2.
A 1.0 kg book is then added to the stack. The same force
is applied, and now the stack accelerates at 2.0 m/s2.
What was the mass of the original stack?
03
m
mm
a1
a2
F
F 21 amΔmmaF
21
2aa
maΔm
22
2
m/s 2.0m/s 3.0
m/s 2.0 kg 1.0
kg 0.2m
maF
Newton’s 2nd Law
A person of weight 480 N stands on a scale in an elevator.
What will the scale be reading when the elevator is
accelerating downward at 4.00 m/s2?
04
aN
W
gW
m
maNW
ga
1WN
agW
NW
2
2
m/s 9.8
m/s 4.01N 480
N 284N
maF
Newton’s 2nd Law
mgW
Weight
A person on a scale rides in an elevator. If the mass of the
person is 60.0 kg and the elevator accelerates downward
with an acceleration of 4.90 m/s2, what is the reading on
the scale?
05
aN
mg
maNmg
agmN 22 m/s 4.9m/s 9.8kg 60
N 294N
maF
Newton’s 2nd Law
A person on a scale rides in an elevator. If the mass of the
person is 60.0 kg and the elevator accelerates upward with an
acceleration of 4.90 m/s2, what is the reading on the scale?
06
aN
mg
mamgN
agmN 22 m/s 4.9m/s 9.8kg 60
N 882N
maF
Newton’s 2nd Law
An object of mass 6000 kg rests on the flatbed of a truck.
It is held in place by metal brackets that can exert a
maximum horizontal force of 9000 N. When the truck is
traveling 15 m/s, what is the minimum stopping distance if
the load is not to slide forward into the cab?
07
voF
m
xmF
2v0 2o
maF
F2
mvx
2o
mF
a
N 9,000 2
m/s 15 kg 6,000 2 m 75
ax2vv 2o
2
Kinematics
maF
Newton’s 2nd Law
xa2v0 2o
In the Atwood machine shown in the
diagram, if m1 = 0.40 kg and m2 = 0.60 kg,
what is the magnitude of the acceleration of
the system? (Ignore friction and the mass
of the pulley.)
08
m1
m2a
m1gm2g
TT
mass 1 mass 2amgmT 11 amTgm 22
amgmT 11 amgmT 22
amgmamgm 2211
21
12mm
gmma
kg 60.0kg 40.0m/s 9.8 kg 40.0kg 60.0 2
2m/s 2.0
maF Newton’s 2nd Law
A 10-kg box sitting on a horizontal surface is pulled by
a 5.0-N force. A 3.0-N friction force retards the motion.
What is the acceleration of the object?
09
Ffm
mafF
mfF
a
kg 10N 0.3N 0.5 2m/s 20.0
maF
Newton’s 2nd Law
In the Atwood machine shown in the
diagram, if m1 = 0.40 kg and m2 = 0.60 kg,
what is the tension in the string? (Ignore
friction and the mass of the pulley.)
10
mass 1 mass 2amgmT 11 amTgm 22
1
1m
gmTa
2
2m
Tgma
21
21mm
gmm2T
kg 60.0kg 40.0m/s 9.8 kg 60.0kg 40.02 2
N 4.7
2
2
1
1m
Tgm
m
gmT
m1
m2a
m1gm2g
TT
maF Newton’s 2nd Law
A student pulls a box of books on a smooth horizontal floor
with a force of 100 N in a direction of 37° above the
horizontal. If the mass of the box and the books is 40.0 kg,
what is the acceleration of the box?
11
m
F
xmaθcosF
mθcosF
ax kg 40
37cosN 100 o 2/sm .02
maF
Newton’s 2nd Law
A traffic light of weight 100 N is supported by two
ropes as shown in the diagram. What are the tensions
in the ropes?
37o 37o
12
T T
W
0WθsinT2
θsin2W
T o37sin2
N 100 N 83
0Fy
Vertical Forces
Two boxes of masses m and 2m are in contact with
each other on a frictionless surface. A force F is
applied to the smaller block as shown in the diagram.
What is the acceleration of the more massive box?
m2mF
13
Both boxes move with the same acceleration
am2mF
m3F
a
amF s
maF
Newton’s 2nd Law
An object slides on a level surface in the +x
direction. It slows and comes to a stop with a
constant acceleration of 2.45 m/s2. What is the
coefficient of kinetic friction between the object and
the floor?
14
mfk
a
mafk mgμf kk
mamgμk
ga
μk 2
2
m/s 8.9
m/s 45.2 25.0
Nμf kk
Friction
maF Newton’s 2nd Law
During a hockey game, a puck is given an initial speed
of 10 m/s. It slides 50 m on the ice before it stops.
What is the coefficient of kinetic friction between the
puck and the ice?
15
x
vo afk
mgμf kk mafk
mamgμk
gμa k
xgμ2v0 k2o
gx2
vμ
2o
k
m 05m/s 9.8 2
m/s 10μ
2
2
k 10.0
xa2v0 2o
v = 0
ax2vv 2o
2
Kinematics
maF
Newton’s 2nd Law
Nμf kk
Friction
During the investigation of a traffic accident, police find
skid marks 90.0 m long. They determine the coefficient of
friction between the car's tires and the roadway to be 0.500
for the prevailing conditions. Estimate the speed of the car
when the brakes were applied.
16
xa2v0 2o
vo
x
fk
mgμf kk mafk
mamgμk
gμa k xgμ2v0 k
2o
gxμ2v ko
m 90 m/s 9.8 0.500 2v 2o m/s 29.7
v = 0a
ax2vv 2o
2
Kinematics
maF Newton’s 2nd Law
Nμf kk Friction
Boxes of masses m and 3m are pulled to the right by a
constant force F as shown in the diagram. The surface
between the more massive box and the horizontal surface is
smooth and the surface between the boxes is rough. If the
less massive box does not slide on the more massive box, what
is the static friction force acting on the less massive box?
F
17
am4F
m4F
a
m fs
maF
m4F
mfk
4F
fk
m
3m
maF
Newton’s 2nd Law
A 10-kg mass slides down a flat hill that makes an
angle of 10° with the horizontal. If friction is
negligible, what is the resultant force on the sled?
18
x
y
mg
NN
mg
mg sin
o2net 10sin 9.8m/s kg 10F
N 17Fnet
Vector Addition
An object with a mass m slides down a rough 37° inclined
plane where the coefficient of kinetic friction is 0.20. What
is the acceleration of the object?
19
x
y
mg
Nfk
θcosmgμf kk
0θcosmgN
θcosmgN xk mafθsinmg
xk maθcosmgμθsinmg
θcosμθsinga kx
oo2x 37cos20.037sinm/s 9.8a
2x m/s 4.3a
xx maF
Newton’s 2nd LawNμf kk
Friction 0Fy Normal Force
An object is placed on an inclined plane. The angle of incline is gradually increased until the object begins to slide. The angle at which this occurs is θ. What is the coefficient of static friction between the object and the plane?
20
0θcosmgN
θcosmgN Nμf ss
θcosmgμf ss 0fθsinmg s
0θcosmgμθsinmg s
θcosθsin
μs θtan
x
y
mg
Nfs
0Fy Normal Force
0Fx X Forces
Nμf ss Static Friction