Download Question 7 - Flipped Physics

AP Quarter 1 Test – Kinematics, Forces and Circular Motion
Question 1 (2001B1). A ball of mass M is attached to a string of length R and negligible mass. The ball moves
clockwise in a vertical circle, as shown above. When the ball is at point P, the string is horizontal. Point Q is at the
bottom of the circle and point Z is at the top of the circle. Air resistance is negligible. Express all algebraic answers
in terms of the given quantities and fundamental constants.
a.
On the figures below, draw and label all the forces exerted on the ball when it is at points P and Q,
respectively.
b. Derive an expression for vmin the minimum speed the ball can have at point Z without leaving the circular path.
c. The maximum tension the string can have without breaking is Tmax Derive an expression for vmax, the
maximum speed the ball can have at point Q without breaking the string.
d. Suppose that the string breaks at the instant the ball is at point P. Describe the motion of the ball
immediately after the string breaks.
Question 2 (1998B1) Two small blocks, each of mass m, are connected by a string of constant length 4h and
negligible mass. Block A is placed on a smooth tabletop as shown above, and block B hangs over the edge of the
table. The tabletop is a distance 2h above the floor. Block A is then released from rest at a distance h above the
floor at time t = 0. Express all algebraic answers in terms of h, m, and g.
a. Determine the acceleration of block A as it descends.
b. Block B strikes the floor and does not bounce. Determine the time t = t 1 at which block B strikes the floor.
c. Describe the motion of block A from time t = 0 to the time when block B strikes the floor.
d. Describe the motion of block A from the time block B strikes the floor to the time block A leaves the table.
e. Determine the distance between the landing points of the two blocks.
3.
A 2 kg object moves in a circle of radius 4 m at a constant speed of 3 m/s. A net force of 4.5 N acts on
the object. What is the angular momentum of the object with respect to an axis perpendicular to the circle
and through its center?
(A) 9 N m/kg
(B) 12 m2/s
(C) 13.5 kg m2/s2
(D) 18 N m/kg
(E) 24 kg m2/s.
4.
Three forces act on an object. If the object is in translational equilibrium, which of the following must be true?
I. The vector sum of the three forces must equal zero.
II. The magnitudes of the three forces must be equal.
III. All three forces must be parallel.
(A) I only
(B) II only
(C) I and III only
(D) II and III only
(E) I, II, and III
5.
An object has a weight W when it is on the surface of a planet of radius R. What will be the gravitational force
on the object after it has been moved to a distance of 4R from the center of the planet?
(A) 16W
(B) 4W
(C) W
(D) 4
(E) 1/16 W
6.
Mars has a mass 1/10 that of Earth and a diameter 1/2 that of Earth. The acceleration of a falling body near the
surface of Mars is most nearly
(A) 0.25 m/s2
(B) 0.5 m/s2
(C) 2 m/s2
(D) 4 m/s2
(E) 25 m/s2
Question 7
Three objects can only move along a straight, level path. The graphs below show the position d of each of the
objects plotted as a function of time t.
7.
8.
The sum of the forces on the object is zero in which of the cases?
(A) II only
(B) III only
(C) I and II only
(D) I and III only
(E) I, II, and III
A wheel of radius R and negligible mass is mounted on a horizontal frictionless axle so that the wheel is in a
vertical plane. Three small objects having masses m, M, and 2M, respectively, are mounted on the rim of the
wheel, as shown above. If the system is in static equilibrium, what is the value of m in terms of M ?
(A) M/2
(B) M
(C) 3M/2
(D) 2M
(E) 5M/2
Questions 9
A rock of mass m is thrown horizontally off a building from a height h, as shown above. The speed of the rock as it
leaves the thrower’s hand at the edge of the building is v0.
9.
How much time does it take the rock to travel from the edge of the building to the ground?
(A)
hv o
(B)
h
v0
(C)
hv 0
g
(D)
2h
g
(E)
2h g
10. A rod on a horizontal tabletop is pivoted at one end and is free to rotate without friction about a vertical axis, as
shown above. A force F is applied at the other end, at an angle  to the rod. If F were to be applied
perpendicular to the rod, at what distance from the axis should it be applied in order to produce the same
torque?
(A) L sin 
(B) L cos 
(C) L
(D) L tan 
(E)
2 L
11. In which of the following situations would an object be accelerated?
I. It moves in a straight line at constant speed.
II. It moves with uniform circular motion.
III. It travels as a projectile in a gravitational field with negligible air resistance.
(A) I only (B) III only (C) I and II only (D) II and III only (E) I, II, and III.
12. A ball falls straight down through the air under the influence of gravity. There is a retarding force F on the ball
with magnitude given by F = bv, where v is the speed of the ball and b is a positive constant. The magnitude of
the acceleration a of the ball at any time is equal to which of the following?
(A) g - b
(B) g - bv/m
(C) g + bv/m
(D) g/b
(E) bv/m
13. A block of weight W is pulled along a horizontal surface at constant speed v by a force F, which acts at an angle
of  with the horizontal, as shown above. The normal force exerted on the block by the surface has magnitude
(A) W - F cos
(B) W-Fsin
(C) W
(D) W + Fsin
(E) W + Fcos
14. If Spacecraft X has twice the mass of Spacecraft Y, then true statements about X and Y include which of the
following?
I. On Earth. X experiences twice the gravitational force that Y experiences.
II. On the Moon, X has twice the weight of Y.
III. When both are in the same circular orbit, X has twice the centripetal acceleration of Y.
(A) I only (B) III only (C) I and II only (D) II and III only (E) I, II, and III
15. The two spheres pictured above have equal densities and are subject only to their mutual gravitational
attraction. Which of the following quantities must have the same magnitude for both spheres?
(A) Acceleration
(B) Velocity
(C) Kinetic energy
(D) Displacement from the center of mass
(E) Gravitational force
16. An automobile moves at constant speed down one hill and up another hill along the smoothly curved surface
shown above. Which of the following diagrams best represents the directions of the velocity and the
acceleration of the automobile at the instant that it is at the lowest position. as shown?
v
v
a
(A)
(B)
a
v
(C)
a
(D)
v
a
v
(E)
a
17. A block of mass 3m can move without friction on a horizontal table. This block is attached to another block of
mass m by a cord that passes over a frictionless pulley, as shown above. If the masses of the cord and the pulley
are negligible, what is the magnitude of the acceleration of the descending block?
(A) Zero
(B) g/4
(C) g/3
(D) 2g/3
(E) g
18. A car initially travels north and then turns to the left along a circular curve. This causes a package on the seat of
the car to slide toward the right side of the car. Which of the following is true of the net force on the package
while it is sliding?
(A) The force is directed away from the center of the circle.
(B) The force is directed north.
(C) There is not enough force directed north to keep the package from sliding.
(D) There is not enough force tangential to the car's path to keep the package from sliding.
(E) There is not enough force directed toward the center of the circle to keep the package from sliding.
19. The planet Mars has mass 6.4 x 1023 kilograms and radius 3.4 x 106 meters. The acceleration of an object in
free-fall near the surface of Mars is most nearly
(A) zero
(B) 1.0 m/s2
(C) 1.9 m/s2
(D) 3.7 m/s2
(E) 9.8 m/s2
20. Two objects, of masses 6 and 8 kilograms, are hung from the ends of a stick that is 70 centimeters long and has
marks every 10 centimeters, as shown above. If the mass of the stick is negligible, at which of the points
indicated should a cord be attached if the stick is to remain horizontal when suspended from the cord?
(A) A
(B) B
(C) C
(D) D
(E) E
Questions 22
A plane 5 meters in length is inclined at an angle of 37°, as shown above. A block of weight 20 newtons is placed
at the top of the plane and allowed to slide down.
21. The mass of the block is most nearly
(A) 1.0 kg
(B) 1.2 kg
(C) 1.6 kg
(D) 2.0 kg
(E) 2.5 kg
22. The displacement x of an object moving along the x-axis is shown above as a function of time t. The
acceleration of this object must be
(A) zero
(B) constant but not zero
(C) increasing
(D) decreasing
(E) equal to g
23. The horizontal turntable shown above rotates at a constant rate. As viewed from above, a coin on the turntable
moves counterclockwise in a circle as shown. Which of the following vectors best represents the direction of the
frictional force exerted on the coin by the turntable when the coin is in the position shown?
(A)
(B)
(C)
(D)
(E)
24. A satellite of mass M moves in a circular orbit of radius R at a constant speed v Which of the following must be
true?
I. The net force on the satellite is equal to MR and is directed toward the center of the orbit.
II. The net work done on the satellite by gravity in one revolution is zero.
III. The angular momentum of the satellite is a constant.
(A) I only (B) III only (C) I and II only (D) II and III only
(E) I, II, and III
25. When an object of weight W is suspended from the center of a massless string as shown above. the tension at
any point in the string is
(A) 2Wcos
(B) ½Wcos
(C) Wcos
(D) W/(2cos)
(E) W/cos
26. A uniform rope of weight 50 newtons hangs from a hook as shown above. A box of weight 100 newtons hangs
from the rope. What is the tension in the rope?
(A) 50 N throughout the rope
(B) 75 N throughout the rope
(C) 100 N throughout the rope
(D) 150 N throughout the rope
(E) It varies from 100 N at the bottom of the rope to 150 N at the top.
27. To weigh a fish a person hangs a tackle box of mass 3.5 kilograms and a cooler of mass 5 kilograms from the
ends of a uniform rigid pole that is suspended by a rope attached to its center. The system balances when the
fish hangs at a point 1/4 of the rod’s length from the tackle box. What is the mass of the fish?
(A) 1.5 kg
(B) 2 kg
(C) 3 kg
(D) 6 kg
(E) 6.5 kg