Download Test 2 Review Test 2 Review (15-16)

Test 2 Review
AP Physics/MTHS/Matthews
Name _______________________
Directions: Answer the following multiple choice questions on this sheet of paper. The answer key will be posted two days before the
test. Please come to class Thursday with questions for Mr. Matthews.
(1) State whether the following are True (T) or False (F).
__________ Inertia is a measure of how difficult it is to change the velocity of an object.
__________ A sled slides down a hill and onto flat ground. Once on flat ground, the force it experienced by the hill’s slope remains in
the sled and is responsible for continuing its motion on the flat ground.
__________ Hansel is running toward Gretel to greet her. In his excitement, Hansel tackles Gretel and knocks her to the floor. During
the interaction, Hansel applies a force to Gretel. Since Gretel flew back Hansel must have hit her harder than she hit him.
__________ A contact force results from the physical contact between two objects.
__________ Third Law Force Pairs can be exerted on the same object, shown in one free-body diagram.
__________ Weight is another way of describing the gravitational force exerted on an object by the Earth.
(2) A crazed dad takes his family on a camping trip. In his packing madness, he loads the top of his 745 kg car with 82.5 kg of
firewood. On top of the firewood, he stacks his 22.0 kg cooler. Draw complete free body diagrams for the car, the wood, and the
cooler.
Car
Wood
Cooler
(3) ____________ A car is traveling on a level highway at a constant velocity in a straight line. Air resistance is present.
Which of the following is the correct free-body force diagram for the car?
(4) A crane lifts up a 200 kg cargo box with an 850 kg Mini Cooper. The Cooper accelerates upward at 2.50 m/s2.
a. Draw a complete free body diagram for the box
b. Determine the force of tension in the crane’s chain.
c. If tension force remains the same but the cargo box now contains a more massive Monster Truck, what
happens to the acceleration of the system? Explain your reasoning.
(5) __________Two blocks are connected by a string and pulley as shown.
Assuming that the string and pulley are massless and frictionless, the tension in the
string is:
A) zero
B) 4.9 N
C) 9.8 N
D) 19.6 N
Picture for questions 5 and 6
E) none of these
(6) __________Two blocks are connected by a string and pulley as shown above.
Assuming that the string and pulley are massless and frictionless, the net force
acting on the block on the left is:
A) zero
B) 4.9 N up
C) 9.8 N up
D) 9.8 N down
E) none of these
(7) __________ A horizontal force of 10.0 N is acting on a
10 kg box that is sliding to the right along the floor with
velocity v (as depicted in the adjacent figure). The
coefficient of kinetic friction between the box and the floor is
0.20. The box is moving with
A) acceleration to the left.
B) acceleration to the right
C) constant speed and constant velocity.
D) constant speed but not constant velocity.
E) no answer is possible
(8) __________Imagine that you are holding an object, of mass m, stationary in your hand. (The weight of the object is
mg.) The net force exerted on the object is:
A) mg upward B) mg downward
C) zero
D) mg + ma upward
E) more information is needed
(9) ____________Two blocks are pushed along a horizontal
frictionless surface by a force of 20 newtons to the right, as
shown. The force that the 2-kilogram block exerts on the
3-kilogram block is
A) 8 newtons to the left
B) 8 newtons to the right
C) 10 newtons to the left
D) 12 newtons to the right
E) 20 newtons to the left
(10) ______________ An object of mass M is suspended from a spring. The extension of the spring is e. The same object is
suspended from an identical spring on the Moon where the acceleration of free fall is less than that on Earth. Which of the
following is correct?
(11) ____________ Two 0.60-kilogram objects are connected by a thread that
passes over a light, frictionless pulley, as shown above. The objects are
initially held at rest. If a third object with a mass of 0.30 kilogram is added
on top of one of the 0.60 kilogram objects as shown and the objects are
released, the magnitude of the acceleration of the 0.30kilogram object is
most nearly
A) 10.0 m/s2
B) 6.0 m/s2
C) 3.0 m/s2 D) 2.0 m/s2
E) 1.0 m/s2
(12) __________ What will be the new tension in the string once the 0.30 kg mass was transferred?
(A) 1.2 N
(B) 4.8 N
(C) 6.0 N
(D) 7.2 N
(E) None of these
Free Response Section
A rope of negligible mass passes over a pulley of negligible mass attached
to the ceiling, as shown above. One end of the rope is held by Student A of
mass 70 kg, who is at rest on the floor. The opposite end of the rope is held
by Student B of mass 60 kg, who is suspended at rest above the floor.
a. On the dots below that represent the students, draw and label free-body
diagrams showing the forces on Student A and on Student B.
b.
Calculate the magnitude of the force exerted by the floor on Student A.
c.
Student B now climbs up the rope at a constant acceleration of 0.25 m/s 2 with respect to the floor.
Calculate the tension in the rope while Student B is accelerating. (hint: I recommend a new FBD)
d.
As Student B is accelerating, is Student A pulled upward off the floor? Justify your answer with numerical proof. (FBD?)
e.
With what minimum acceleration must Student B climb up the rope to lift Student A upward off the floor? (What will be “FN”?)
A student of mass m stands on a platform scale in an elevator in a tall building. The positive direction for all vector quantities is
upward.
a.
Draw a free-body diagram showing and labeling all the forces acting on the student, who is represented by the dot below.
b.
Derive an expression for the reading on the scale in terms of the acceleration a of the elevator, the mass m of the student, and “g”.
An inspector provides the student with the following graph showing the acceleration “a” of the elevator as a function of time t.
c. During what time interval(s) is the speed of the elevator constant? What will the scale read during these time intervals?
d.
i. During what time interval(s) is the force exerted by the platform scale on the student a maximum value? Explain & show an
FBD at this time.
ii.
Calculate the magnitude of that maximum force by the scale on the 45 kg student.