Download AP Physics C Laws of Motion MC Sample Test

AP Physics C
Laws of Motion
MC Sample Test
1.
Which of these is true about mass?
I. It is the amount of matter an object consists of.
II. It is an objects weight.
III. Inertia is a consequence of having mass.
IV. It changes with the strength of gravity g.
(A) I only.
(B) II only.
(C) I and II.
(D) I and III.
(E) All of these are true for mass.
7.
An object initially at rest moves a distance x when a force
F is applied for a time t. How far will the object move if
a force of 2F is applied for the same time t ?
2
(A)
x
2
2x
(B)
(C) 2x
(D) 2 2x
(E) 4x
2.
The tendency of objects to maintain their velocity is
caused by
(A) force and stated in Newton’s 1st Law.
(B) force and stated in Newton’s 2nd Law.
(C) inertia and stated in Newton’s 2nd Law.
(D) mass and stated in Newton’s 1st Law.
(E) impedus and stated in Newton’s 1st Law.
8.
A 10 kg mass is accelerated upward by a rope at 2 m/s2.
The tension in the rope is
(A) 50 N.
(B) 80 N.
(C) 100 N.
(D) 120 N.
(E) 200 N.
3.
Starting a vehicle moving from rest on a horizontal surface
on the moon requires
(A) the same forward force.
(B) less forward force, since mass on the moon is
smaller.
(C) less forward force, since weight on the moon is
smaller.
(D) more forward force, due to the absence of an
atmosphere.
(E) Requires more information to answer.
9.
The space shuttle increases its acceleration every second
during take off, even though its engines generate the same
amount of force. Which off these contributes the most
significantly to this effect?
(A) Gravity g is decreasing.
(B) It is losing mass as it burns fuel.
(C) The air gets thinner at higher altitudes.
(D) Acceleration increases since the engines have burned
for a longer period of time.
4.
Two different objects have the same density and both
weigh 100 N. However, one is on a planet where gravity is
greater than on earth. Which object is larger?
(A) Mass of a single object does not change from planet
to planet.
(B) The object on Earth is larger.
(C) The object on the other planet is larger.
(D) The scales read incorrectly due to the gravity change,
and both objects are the same size.
(E) Not enough information to say.
5.
Which is true regarding an objects weight?
I. It is the same everywhere regardless of gravity.
II. It is a scalar, while mass is a vector.
III. It is the force acting on mass in a gravity field.
IV. It is the same as mass. The force of gravity is g.
(A) I only.
(B) II only.
(C) III only.
(D) IV only.
(E) I and IV.
6.
In balanced force problems, which can be determined
conclusively?
(A) the object is at rest.
(B) the object is at constant nonzero velocity.
(C) there is a net force acting on the object.
(D) the sum of force vectors is zero.
(E) None of the above.
10. When an object is thrown upward, in the absence of air
resistance, and reaches the top of its trajectory it stops
instantaneously. At this point the net force acting on the
object is
(A) g
(B) zero.
(C) the objects weight.
(D) the objects mass.
(E) changing directions
11. Two objects with different masses are dropped from the
same height with no air resistance. They reach the ground
at the same time because
(A) mass is not a factor and thus has no effect on
acceleration.
(B) the more massive object has more inertia and requires
more force to accelerate at the same rate.
(C) the same net force acts on both objects, creating the
same acceleration.
(D) weight is not a factor in acceleration of dropped
objects.
(E) This does not happen. The heavier object strikes the
ground first.
12. A small object with a weight of 50 N is experiencing the
gravitational force of the entire Earth. The object pulls
back on the Earth with a force of
(A) 0 N.
(B) Non zero force, but small enough to be negligible.
(C) 5 N.
(D) 50 N.
(E) 500 N.
13. In a tug of war both sides of the rope are pulled with a
force of 500 N. Then tension in the rope is
(A) 0 N.
(B) 50 N.
(C) 250 N.
(D) 500 N.
(E) 1000 N.
14. A rocket moves upward during its launch. Which of these
is true?
(A) Exhaust gases push on the Earth creating an equal
and opposite upward force.
(B) Exhaust gases push on air molecules creating an
equal and opposite upward force.
(C) Exhaust gases pushed backwards by the rocket are
the action force, and the rocket moving in the
opposite direction is the reaction force.
(D) The force of the exhaust gases must be small so that
they don’t add too much downward force to gravity.
If they do the rocket will not have enough upward
force.
(E) All of these are incorrect.
15. When you push on an object the reaction force depends on
(A) the object’s mass.
(B) your mass.
(C) the objects speed.
(D) your speed.
(E) None of these.
16. A 70 kg person stands on a scale in an elevator that is
accelerating upward at 2 m/s2. What does the scale report?
(A) 560 N.
(B) 700 N.
(C) 840 N.
(D) 960 N.
(E) 1000 N.
17. A 70 kg person stands on a scale in an elevator that is
moving at constant downward velocity of 2 m/s. What
does the scale report?
(A) 560 N.
(B) 700 N.
(C) 840 N.
(D) 960 N.
(E) 1000 N.
18. When an object hangs at static equilibrium from two ropes,
which of the following is true in every possible case?
(A) Each rope supports the objects weight.
(B) The tension in the two ropes adds to the objects total
weight.
(C) The vertical components of each ropes tension
support half the objects weight.
(D) The vertical components of tension add together to
equal the objects weight.
(E) Each of these covers a special case, but none covers
every possible problem of this type.
19. The amount of friction acting on a mass is influenced by
I. the roughness of the surface.
II. the size of the surfaces rubbing against one
another.
III. the force that the surfaces press against each
other with.
(A) I only.
(D) I and II
(B) II only.
(E) I and III
(C) III only.
20. You need to buy new tires for your car. Of the available
tires listed below, which are the best for stopping quickly
in an emergency?
(A) Expensive brand name wide sports car tires with a
coefficient of friction of 0.80.
(B) Medium width and mid-price tires with a coefficient
of friction of 0.80.
(C) Incredibly narrow tires with a bargain basement
price, and a coefficient of friction of 0.80.
(D) All will stop equally well.
Use the following diagram for questions 21 to 23
F
21. A mass has a horizontal force F applied to it, but remains
standing still due to the roughness of the surface. We can
definitely conclude that the force of friction is equal to
(A) zero.
(D) Both A and C
(E) Both B and C
(B) µmg
(C) F
22. A mass m is pulled along a rough horizontal surface as
shown above. If the mass is moving at constant velocity,
then the friction force f must be
(A) zero.
(D) Both A and C
(B) µmg
(E) Both B and C
(C) F
23. A mass m is pulled at along a rough horizontal surface as
shown above. If the mass is accelerating, then friction must
be
(A) zero.
(D) Both A and C
(B) µmg
(E) Both B and C
(C) F
Use the following diagram for questions 24 and 25
F
θ
24. A mass m is pulled along a horizontal surface by force F
as shown. If the resulting motion is constant velocity, then
the frictional force must be
(A) zero.
(D) Fcosθ
(E) Fsinθ
(B) µmg
(C) µmgcosθ
25. A mass m is pulled along a horizontal surface by force F
as shown above. If the mass is accelerating, then the
frictional force must be
(A) zero.
(D) Fcosθ
(E) µ ( mg − F sin θ )
(B) µmg
(C) µmgcosθ
Use the following diagram for questions 26 to 27
Use the following diagram for questions 31 and 32
m
m
θ
26. Mass m slides down an incline with slope θ as shown
above. Under which circumstances does µs = tan θ hold
true.
I. At all angles that result in the mass being at rest.
II. At the angle where the block just begins to
move.
III. At the angle where the block moves at constant
velocity.
IV. At the angle where the block accelerates.
(A) I only.
(D) IV only.
(B) II only.
(E) II and III.
(C) III only.
27. Mass m slides down an incline with slope θ as shown
above. Under which circumstances does µk = tan θ hold
true.
I. At all angles that result in the mass being at rest.
II. At the angle where the block just begins to
move.
III. At the angle where the block moves at constant
velocity.
IV. At the angle where the block accelerates.
(A) I only.
(D) IV only.
(B) II only.
(E) III and IV.
(C) III only.
28. A mass m slides down a rough incline at constant
velocity. The slope angle is θ and the coefficient of
friction is µ. Which of the following statements is NOT
true?
(A) The normal force is mg cos θ
(B) The force of gravity is mg sin θ
(C) The force of friction is µmg cos θ
(D) The coefficient of friction is tan θ
(E) All are true.
Use the following diagram for questions 29 and 30
m1
m2
m3
F
29. Masses m1 = 3 kg, m2 = 2 kg, and m3 = 1 kg are
connected by massless strings, and a force F = 24 N pulls
the system to the right along a frictionless surface as
shown above. What is the systems acceleration?
(A) 0 m/s2
(D)
6 m/s2
2
(B) 2 m/s
(E)
8 m/s2
2
(C) 4 m/s
30. Masses m1 = 3 kg, m2 = 2 kg, and m3 = 1 kg are
connected by massless strings, and a force F = 24 N pulls
the system to the right along a frictionless surface as
shown above. What is the tension in the string between m2
and m3?
(A) 1 N
(D) 12 N
(B) 4 N
(E) 20 N
(C) 8 N
2m
31. Mass m moves horizontally along a frictionless table top,
while mass 2m hangs vertically. The string between them
is massless, and the pulley is massless and frictionless. The
acceleration of the system is
1
(A) 3mg
(D)
g
2
2
1
(E)
g
(B)
mg
3
2
2
(C)
mg
3
32. Mass m moves horizontally along a frictionless table top,
while mass 2m hangs vertically, as shown above. The
string between them is massless, and the pulley is massless
and frictionless. Using the acceleration from the problem
above solve for the tension in the string.
1
(A) 3mg
(D)
g
2
1
2
(B)
(E)
g
mg
2
3
2
(C)
mg
3
Use the following diagram for questions 33 and 34
2m
m
33. Mass 2m lies on a horizontal rough table top, while mass
m hangs vertically. The string between them is massless,
and the pulley is massless and frictionless. What
coefficient of friction will keep the system at rest?
(A) 0 2
(D) 0.6
(B) 0.4
(E) 0.8
(C) 0.5
34. Mass 2m is on a rough horizontal surface, while mass m
hangs vertically. Friction on the surface keeps the system
at rest. Determine tension in the string?
(A) zero
(D) 3mg
(B) mg
(E) 4mg
(C) 2mg
m
38. When one object, mass m, orbits another it is the gravity
of the central object that provides the centripetal force. If
the orbiting object is a distance r from the central object,
what is its speed?
(A) zero
rg
(B)
2m
2rg
(C)
(D) 2rg
(E) 2mrg
35. Masses m and 2m are attached by a massless string over
a massless frictionless pulley. Determine the acceleration
of the system.
1
(A) 3mg
(D)
g
3
1
1
(B)
(E)
g
mg
3
2
1
(C)
mg
2
39. A rollercoaster, mass m, just barely completes a loop.
What is the speed at the top of the loop?
(A) zero
(B)
rg
36. In uniform circular motion, which vectors point toward the
center of the circle?
(A) Centrifugal acceleration and centrifugal force.
(B) Centrifugal acceleration and centripetal force.
(C) Centripetal acceleration and centrifugal force.
(D) Centripetal acceleration and centripetal force.
(E) Velocity.
40. How fast must a rollercoaster be moving at the top of the
loop so that the occupants feel weightless?
(A) zero
(B)
rg
37. An object is moving in uniform circular motion. If the
speed is doubled and the radius doubled the force and
acceleration will
(A) double.
(B) be cut in half.
(C) not change.
(D) quadruple.
(E) will be 2 time larger.
1.
2.
3.
4.
5.
6.
7.
D
D
A
B
C
D
C
8.
9.
10.
11.
12.
13.
14.
D
B
C
B
D
D
C
15.
16.
17.
18.
19.
20.
21.
E
C
B
D
E
D
C
2rg
(C)
(D) 2rg
(E) 2mrg
2rg
(C)
(D) 2rg
(E) 2mrg
41. A car completes a turn of radius 20 m at a uniform speed
of 10 m/s. What minimum coefficient of friction can the
tires have?
(A) 0.1
(D) 0.5
(B) 0.2
(E) 1.0
(C) 0.4
22.
23.
24.
25.
26.
27.
28.
E
B
D
E
B
C
B
29.
30.
31.
32.
33.
34.
35.
C
E
E
C
C
B
D
36.
37.
38.
39.
40.
41.
D
A
B
B
B
D