PHY 111 Final Exam Questions With Complete Solutions
A 0.15 kg arrow moving with an initial velocity of 30 m/s passes
through a 3.0 kg block initially at rest on a frictionless surface. If
the final speed of the arrow is 25 m/s, what is the speed of the
block? Correct Answers 0.25 m/s
A 1.0 kg piece of putty initially moves with a velocity of 1.0 m/s
to the right. The putty collides with and sticks to a 5.0 kg ball
initially at rest. Assuming negligible friction, which of the
following best describes the momentum of the system after the
collision? Correct Answers Equal to 1.0 kg-m/s
A 15 kg ladder with a length of 2.0 m is placed against a smooth
wall. The ladder forms an angle of 75° relative to the ground.
What is the friction force on the ladder? Correct Answers 19.7
N
A 2.0 kg bar with a length of 1.4 m is attached to a wall with a
swivel mount. A 5.0 kg mass is suspended from the bar at a
position 0.8 m from the pivot. The other end of the bar is held by
a rope, which is attached vertically to the ceiling. What is the
tension force in the rope? Correct Answers 37.8 N
A 25 kg child rides a 3.0 kg skateboard with an initial velocity
of 2.0 m/s. The child jumps backward off the skateboard in such
a way that she has no final velocity. What is the resulting speed
of the skateboard? Correct Answers 18.7 m/s
A 50 kg solid disk (I = 1/2mr^2) with a radius of r = 3.5 m starts
from rest and rotates about an axis through its center. It takes 30
,rotations to reach an angular velocity of ω = 16 rad/s. [θ = 35°]
What is the disk's angular acceleration?
b) How much time does it take to reach the final velocity?
c) What is the net torque on the disk during the acceleration?
d) If the net torque is caused by a single force applied at an
angle of θ = 35° to the rim of the disk, what is the magnitude of
that force? Correct Answers eq: ω2 = 2a∆θ + ω02
where: ω = 16 rad/s, θ = 35°, ω0 = 0 (starts from rest)
(16)^2 = 2a(35) + (0)^2
a = 3.7 rad/s/s
b) eq: ω = at + ω0
where: ω = 16 rad/s, a = 3.7 rad/s/s, ω0 = 0 (starts from rest)
16 = (3.7)t + 0
t = 4.3 seconds
c) eq: ΣT = Ia --> ΣT = ½ (m)(r)^2(a)
where: I = ½ (m)(r)^2 (m = 50 kg, r = 3.5), a = 3.7 rad/s/s
ΣT = (½)(50)(3.5)^2(3.7)
ΣT = 1,133.1 N-m
d) eq: T = rFsin(θ)
, where: T = 1,133.1 N-m, r = 3.5 m, θ = 35°
1,133.1 = (3.5)Fsin(35)
F = 564.4 N
A 60 kg student on the end of a 1.5 m diviner's board. What is
the student's torque on the diving board? Correct Answers 882
m-N
A baseball bat collides with a 0.145 kg baseball moving with an
initial velocity of 35 m/s to the left. If the collision lasts 0.005
seconds and the final velocity of the ball is 25 m/s to the right,
what was the force of the bat on the ball? Correct Answers
1740 N
A bug splats against the windshield of a car traveling at high
speeds down a backcountry road. What statement correctly
compares the objects' changes in momentum? Correct Answers
The bug's change in momentum is equal to the car's change in
momentum
A car turns a corner at a constant speed. Which of the following
correctly identifies all of the non-zero acceleration terms
experienced by the car? Correct Answers Centripetal
A class F model rocket engine can provide an impulse between
40-80 N-s. A student attaches a class F rocket that can apply an
impulse of 60 N-s to a model rocket of mass (m = 2 kg) If the
engine burns for (t = 7 seconds), what is the average engine
thrust provided by the engine?
A 0.15 kg arrow moving with an initial velocity of 30 m/s passes
through a 3.0 kg block initially at rest on a frictionless surface. If
the final speed of the arrow is 25 m/s, what is the speed of the
block? Correct Answers 0.25 m/s
A 1.0 kg piece of putty initially moves with a velocity of 1.0 m/s
to the right. The putty collides with and sticks to a 5.0 kg ball
initially at rest. Assuming negligible friction, which of the
following best describes the momentum of the system after the
collision? Correct Answers Equal to 1.0 kg-m/s
A 15 kg ladder with a length of 2.0 m is placed against a smooth
wall. The ladder forms an angle of 75° relative to the ground.
What is the friction force on the ladder? Correct Answers 19.7
N
A 2.0 kg bar with a length of 1.4 m is attached to a wall with a
swivel mount. A 5.0 kg mass is suspended from the bar at a
position 0.8 m from the pivot. The other end of the bar is held by
a rope, which is attached vertically to the ceiling. What is the
tension force in the rope? Correct Answers 37.8 N
A 25 kg child rides a 3.0 kg skateboard with an initial velocity
of 2.0 m/s. The child jumps backward off the skateboard in such
a way that she has no final velocity. What is the resulting speed
of the skateboard? Correct Answers 18.7 m/s
A 50 kg solid disk (I = 1/2mr^2) with a radius of r = 3.5 m starts
from rest and rotates about an axis through its center. It takes 30
,rotations to reach an angular velocity of ω = 16 rad/s. [θ = 35°]
What is the disk's angular acceleration?
b) How much time does it take to reach the final velocity?
c) What is the net torque on the disk during the acceleration?
d) If the net torque is caused by a single force applied at an
angle of θ = 35° to the rim of the disk, what is the magnitude of
that force? Correct Answers eq: ω2 = 2a∆θ + ω02
where: ω = 16 rad/s, θ = 35°, ω0 = 0 (starts from rest)
(16)^2 = 2a(35) + (0)^2
a = 3.7 rad/s/s
b) eq: ω = at + ω0
where: ω = 16 rad/s, a = 3.7 rad/s/s, ω0 = 0 (starts from rest)
16 = (3.7)t + 0
t = 4.3 seconds
c) eq: ΣT = Ia --> ΣT = ½ (m)(r)^2(a)
where: I = ½ (m)(r)^2 (m = 50 kg, r = 3.5), a = 3.7 rad/s/s
ΣT = (½)(50)(3.5)^2(3.7)
ΣT = 1,133.1 N-m
d) eq: T = rFsin(θ)
, where: T = 1,133.1 N-m, r = 3.5 m, θ = 35°
1,133.1 = (3.5)Fsin(35)
F = 564.4 N
A 60 kg student on the end of a 1.5 m diviner's board. What is
the student's torque on the diving board? Correct Answers 882
m-N
A baseball bat collides with a 0.145 kg baseball moving with an
initial velocity of 35 m/s to the left. If the collision lasts 0.005
seconds and the final velocity of the ball is 25 m/s to the right,
what was the force of the bat on the ball? Correct Answers
1740 N
A bug splats against the windshield of a car traveling at high
speeds down a backcountry road. What statement correctly
compares the objects' changes in momentum? Correct Answers
The bug's change in momentum is equal to the car's change in
momentum
A car turns a corner at a constant speed. Which of the following
correctly identifies all of the non-zero acceleration terms
experienced by the car? Correct Answers Centripetal
A class F model rocket engine can provide an impulse between
40-80 N-s. A student attaches a class F rocket that can apply an
impulse of 60 N-s to a model rocket of mass (m = 2 kg) If the
engine burns for (t = 7 seconds), what is the average engine
thrust provided by the engine?
