phy 111 midterm Questions With Complete Solutions
5. A block slides down an inclined plane at a constant velocity.
Which of the following statements about the friction force is
correct?
a) The friction force is equal to the gravity force.
b) The friction force is equal to the normal force.
c) The friction force is equal to the component of the gravity
force parallel to the ramp.
d) The friction force is equal to the component of the gravity
force perpendicular to the ramp.
Explain your answer. Correct Answers Friction will occur
parallel to the ramp's surface. In order for the block to move at a
constant speed, there must be an equal sized opposing force to
cancel it. This force is the component of gravity that is parallel
to the surface. The correct answer is C.
A 14.0 kg box initially at rest experiences a horizontally applied
force of 8.0 N of force and a friction force of 3.0 N. How long
will it take for the box to move 5.0 m? Correct Answers he
horizontal forces do not cancel. Use Newton's second law.
ΣFx = ma
f + F = ma
(-3.0 N) + (8.0 N) = (14.0 kg)(a)
a = 0.36 m/s/s
x = ½ at2 + vot + xo
(5.0 m) = ½ (0.36 m/s/s)(t2) + 0 + 0
t = 5.3 seconds
,A 500 kg rollercoaster car starts from rest at the top of a 15.0 m
hill. The car travels down the hill, around a loop, and then
travels up a smaller 5.0 m tall hill. What is the speed of the car
when it reaches the top of the second hill? (Ignore friction and
air resistance.)
b) The second hill has a flat straight-away that ends with a very
large spring. How much will the car compress the spring if the
spring constant is 3000 N/m? Correct Answers Ug = K + Ug
(mgh)start = ½ mv^2 + (mgh)end
(500 kg)(9.8 N/kg)(15.0 m) = ½ (500 kg)(v^2) + (500 kg)(9.8
N/kg)(5.0 m)
v = 14 m/s
Ug = Ug + Us
(mgh)start = (mgh)end + ½ kΔx^2
(500 kg)(9.8 N/kg)(15.0 m) = (500 kg)(9.8 N/kg)(5.0 m) + ½
(3000 N/m)(Δx^2)
Δx = 5.7 m
That's a pretty large spring if its compression is nearly 6 m.
A ball is attached to the center of the ceiling inside of a van
moving at constant speed. If the ball is released, where will the
ball land? Correct Answers Directly below its starting position
(middle of the van)
A medium-sized air conditioning unit is rated at 900 W. How
much energy will the AC unit require in order to operate for 2.0
hours? Correct Answers 6.48x10^6 J
, A particular position-time graph is linear with a negative
straight-line slope. This means that the object Correct Answers
is moving backwards
A second satellite is put into orbit around the moon. This
satellite needs to have a shorter period of rotation. Should it
orbit closer to the surface or further from the surface? Explain.
Correct Answers The new satellite should orbit closer to the
surface. The gravitational pull will be greater, and the distance
traveled will be shorter, both of which mean the speed will be
greater. Therefore, it will take less time to orbit.
A student applies a 100 N force at an angle of 30° below the
horizontal. What is the horizontal component of the student's
applied force? Correct Answers 86.6 N
A student applies a constant horizontal 20 N force to a 12 kg
box that is initially at rest. The student moves the box a distance
of 3.0 m. What is the speed of the box at the end of the motion?
Assume negligible friction. Correct Answers 3.2 m/s
0.50 * 12 * v^2 = 20 * 3
solving for v
v = 3.2 m/s
A student attaches a 1.5 kg mass to a spring. When the spring is
released, the mass will fall. The student places a raw egg at a
position 0.70 m below the starting point of the mass. What
spring constant is needed so that the mass will fall, tap the egg
5. A block slides down an inclined plane at a constant velocity.
Which of the following statements about the friction force is
correct?
a) The friction force is equal to the gravity force.
b) The friction force is equal to the normal force.
c) The friction force is equal to the component of the gravity
force parallel to the ramp.
d) The friction force is equal to the component of the gravity
force perpendicular to the ramp.
Explain your answer. Correct Answers Friction will occur
parallel to the ramp's surface. In order for the block to move at a
constant speed, there must be an equal sized opposing force to
cancel it. This force is the component of gravity that is parallel
to the surface. The correct answer is C.
A 14.0 kg box initially at rest experiences a horizontally applied
force of 8.0 N of force and a friction force of 3.0 N. How long
will it take for the box to move 5.0 m? Correct Answers he
horizontal forces do not cancel. Use Newton's second law.
ΣFx = ma
f + F = ma
(-3.0 N) + (8.0 N) = (14.0 kg)(a)
a = 0.36 m/s/s
x = ½ at2 + vot + xo
(5.0 m) = ½ (0.36 m/s/s)(t2) + 0 + 0
t = 5.3 seconds
,A 500 kg rollercoaster car starts from rest at the top of a 15.0 m
hill. The car travels down the hill, around a loop, and then
travels up a smaller 5.0 m tall hill. What is the speed of the car
when it reaches the top of the second hill? (Ignore friction and
air resistance.)
b) The second hill has a flat straight-away that ends with a very
large spring. How much will the car compress the spring if the
spring constant is 3000 N/m? Correct Answers Ug = K + Ug
(mgh)start = ½ mv^2 + (mgh)end
(500 kg)(9.8 N/kg)(15.0 m) = ½ (500 kg)(v^2) + (500 kg)(9.8
N/kg)(5.0 m)
v = 14 m/s
Ug = Ug + Us
(mgh)start = (mgh)end + ½ kΔx^2
(500 kg)(9.8 N/kg)(15.0 m) = (500 kg)(9.8 N/kg)(5.0 m) + ½
(3000 N/m)(Δx^2)
Δx = 5.7 m
That's a pretty large spring if its compression is nearly 6 m.
A ball is attached to the center of the ceiling inside of a van
moving at constant speed. If the ball is released, where will the
ball land? Correct Answers Directly below its starting position
(middle of the van)
A medium-sized air conditioning unit is rated at 900 W. How
much energy will the AC unit require in order to operate for 2.0
hours? Correct Answers 6.48x10^6 J
, A particular position-time graph is linear with a negative
straight-line slope. This means that the object Correct Answers
is moving backwards
A second satellite is put into orbit around the moon. This
satellite needs to have a shorter period of rotation. Should it
orbit closer to the surface or further from the surface? Explain.
Correct Answers The new satellite should orbit closer to the
surface. The gravitational pull will be greater, and the distance
traveled will be shorter, both of which mean the speed will be
greater. Therefore, it will take less time to orbit.
A student applies a 100 N force at an angle of 30° below the
horizontal. What is the horizontal component of the student's
applied force? Correct Answers 86.6 N
A student applies a constant horizontal 20 N force to a 12 kg
box that is initially at rest. The student moves the box a distance
of 3.0 m. What is the speed of the box at the end of the motion?
Assume negligible friction. Correct Answers 3.2 m/s
0.50 * 12 * v^2 = 20 * 3
solving for v
v = 3.2 m/s
A student attaches a 1.5 kg mass to a spring. When the spring is
released, the mass will fall. The student places a raw egg at a
position 0.70 m below the starting point of the mass. What
spring constant is needed so that the mass will fall, tap the egg
