Topic 2 Exam Review

The students double the mass that hangs from the string. They also replace the original cart with a new cart that has double the mass. By doubling both masses, how will the tension in the string and the acceleration of the cart change?

(B) The tension will double, but the acceleration will stay the same.

Two objects of the same mass travel in the same direction along a horizontal surface. Object X has a speed of 5 m/s and object Y has a speed of 2 m/s , as shown in the figure. After a period of time, object X collides with object Y. Consider the situation in which the objects collide but do not stick together. Which of the following predictions is true about the center of mass of the two-object system immediately after the collision?

(B) The velocity of the center of mass does not change.

A block can slide along the frictionless track shown above. A student moves the block along the track so that the block has the same speed at point , point , and point . The work done by the student on the block as it moves from to is most nearly

(C) -12 J

A toy doll and a toy robot are standing on a frictionless surface facing each other. The doll has a mass of, and the robot has a mass of. The robot pushes on the doll with a force of. The magnitude of the acceleration of the robot is

(C) 1.0 m/s^2

The system shown above is released from rest. If friction is negligible, the acceleration of the 4.0 kg block sliding on the table shown above is most nearly

(C) 3.3 m/s^2

Blocks X and Y are glued together and released from rest on a ramp with negligible friction, as shown in trial 1. The blocks are then separated and connected by a light spring, as shown in trial 2. The spring is compressed and the blocks are again released from rest on the ramp. Immediately after the blocks are released, is the net force on the two-block system the same or different between trial 1 and trial 2? Immediately after the blocks are released, is the net force on block Y the same or different between trial 1 and trial 2?

(C) Force on System: The same Force on Block Y: Different

A 50.0 N box is at rest on a horizontal surface. The coefficient of static friction between the box and the surface is 0.50, and the coefficient of kinetic friction is 0.30. A horizontal 20.0 N force is then exerted on the box. The magnitude of the acceleration of the box is most nearly

(A) 0 m/s^2

The free body diagram shown above is for a box on a rough surface being pulled to the right at a constant speed by a string that is at an angle of above the horizontal. The coefficient of kinetic friction between the box and the surface is . The tension in this string is most nearly

(A) 14.47 N

The Atwood's machine shown consists of two blocks of mass and that are connected by a light string that passes over a pulley of negligible friction and negligible mass. The block of mass is a distance above the ground, and the block of mass is a distance above the ground. is larger than . The two-block system is released from rest. Which of the following claims correctly describes the outcome after the blocks are released from rest but before the block of reaches the ground? Select two answers.

(A) For the system consisting of the two blocks, the change in the kinetic energy of the system is equal to the work done by gravity on the system. (D) For the system consisting of the two blocks, the pulley, and Earth, the change in the total mechanical energy of the system is zero.

On a straight horizontal track along which blocks can slide with negligible friction, block 1 slides toward block 2, which is initially at rest. Block 1 collides with an electronic force probe attached to block 2, generating a force vs. time graph and causing block 2 to start sliding. What additional measurements must be made to determine the momentum of block 2 after the collision?

(A) None

The position as a function of time (position vs time) for two objects moving along a straight line is shown in the graph. (Object 1- squiggly graph and Object 2- linear graph) Which statement is true about the distances the two object have traveled at time?

(A) Object 1 has traveled a greater distance.

An object attached to one end of a string moves in a circle at constant speed. Which of the following is correct?

(A) The object is accelerating as it moves.

A ball is tossed straight up and later returns to the point from which it was launched. If the ball is subject to air resistance as well as gravity, which of the following statements is correct?

(A) The speed at which the ball returns to the point of launch is less than its speed when it was initially launched.

Two blocks of masses 1.0 kg and 2.0 kg, respectively, are pushed by a constant applied forceFacross a horizontal frictionless table with constant acceleration such that the blocks remain in contact with each other, as shown above. The 1.0 kg block pushes the 2.0 kg block with a force of 2.0 N. The acceleration of the two blocks is

(B) 1.0 m/s^2

A projectile fired into the air explodes and splits into two halves of equal mass that hit the ground at the same time. If the projectile had not exploded, it would have landed at point X, which is a distance R to the right of the launch point. After the explosion, one of the halves lands at point Y, which is a distance 2R to the right of the launch point. If air resistance is negligible, where did the other half land?

(B) At the launch point

A block of mass and a block of mass are connected by a string, as shown above. The blocks are held with the string horizontally and are released from rest at the same time from a height above the ground. How does the acceleration of the center of mass of the system compare to the acceleration of the object of mass ?

(C) The acceleration of the center of mass is the same as the acceleration of the object of mass .

An inclined track is secured to a table. The height of the highest point of the track above the tabletop is . The height from the tabletop to the floor is . A block of mass is released from rest and slides down the track such that all frictional forces are considered to be negligible. The block leaves the track horizontally and strikes the ground at a distance from the edge of the track as shown. Which of the following statements is correct about the scenario? Select two answers

(C) The total mechanical energy of the system containing only the block increases from the moment of release to the moment it strikes the ground. (D) The total mechanical energy of the block-Earth system remains constant.

Objects X and Y are connected by a string of negligible mass and suspended vertically over a pulley of negligible mass, creating an Atwood's machine, as shown in the figure. The objects are initially at rest, and the mass of Object Y is greater than the mass of Object X. As Object Y falls, how does the gravitational potential energy of the Object X-Object Y-Earth system change? All frictional forces are considered to be negligible.

(D) The gravitational potential energy decreases because the center of mass of Object X and Object Y moves downward.

An object starts from rest and slides with negligible friction down an air track tipped at an angle θ from the horizontal. A student records values of the object's position along the track at various times. The value of θ can best be determined from which of the following?

(D) The slope of a graph of position as a function of the square of time

A person holds a book at rest a few feet above a table. The person then lowers the book at a slow constant speed and places it on the table. Which of the following accurately describes the change in the total mechanical energy of the Earth-book system?

(D) The total mechanical energy decreases, because the person does negative work on the book by exerting a force on the book in the direction opposite to its displacement.

A moon of mass 1 x 10^20 kg is in a circular orbit around a planet. The planet exerts a gravitational force of 2 x 10^21 N on the moon. The centripetal acceleration of the moon is most nearly

20 m/s^2

Balls 1 and 2 are each thrown horizontally from the same height above level ground, but ball 2 has a greater initial velocity after leaving the thrower's hand. If air resistance is negligible, how do the accelerations of the balls and the times it takes them to hit the ground compare?

Acceleration a: equal Time to hit the ground: equal

The stacks of boxes shown in the figure above are inside an elevator that is moving upward. The masses of the boxes are given in terms of the mass M of the lightest box. M 2M 2M 4M M M 2M 2M

Assume the elevator has upward acceleration a, and consider the stack that has two boxes of mass M. What is the magnitude of the force exerted on the top box by the bottom box? - (D) M (a + g) How does the magnitude of the force exerted by the top box on the bottom box compare with the magnitude of the force exerted by the bottom box on the top box for each of the stacks? - (A) The two magnitudes are always equal in each of the stacks.

A railroad car of mass m is moving with speed u when it collides with and connects to a second railroad car of mass 3m, initially at rest, as shown above. How do the speed and kinetic energy of the connected cars compare to those of the single car of mass m before the collision?

Speed: less Kinetic energy: less

Students work together during an experiment about Newton's laws. The students use a setup that consists of a cart of known mass connected to one end of a string that is looped over a pulley of negligible friction, with its other end connected to a hanging mass. The cart is initially at rest on a horizontal surface and rolls without slipping when released. The inertia of the cart's wheels is negligible. Students have access to common laboratory equipment to make measurements of components of the system. By collecting the appropriate data, the students can determine the relationship between the acceleration of the cart and the net force exerted on the cart. Which of the following graphs should the students produce to show the correct relationship?

The graph is an acceleration by net force graph, and the graph is a positive linear graph

The position as a function of time (position vs time) for two objects moving along a straight line is shown in the graph. (Object 1- squiggly graph and Object 2- linear graph) At which of the following times do the two objects have the same velocity?

The time when they have the same slope.

The force diagram above shows a box accelerating to the right on a horizontal surface of non-negligible friction. The tension is exerted at an angle of above the horizontal. If is the coefficient of kinetic friction between the box and the surface, which of the following is a correct mathematical equation derived by applying Newton's second law to the box? Figure: a box is on a table with mg, normal force, friction, and tension at an angle

a = T cos (theta) - friction coefficient (Mg - T sin (theta)) / M