APY1_Unit 6 Review

A dog of mass 10 kg sits on a skateboard of mass 2 kg that is initially traveling south at 2 m/s. The dog jumps off with a velocity of 1 m/s north relative- to the ground. Which of the following is the best estimate of the velocity of the skateboard immediately after the dog has jumped?

• 1 m/s north

• 1 m/s south

• 3 m/s south

• 7 m/s south

• 17 m/s south

A railroad car of mass m is moving with speed v 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; KE Less

• Speed Less; KE Same

• Speed Same; KE Less

• Speed Same; KE Same

• Speed Greater; KE Same

Two people are initially standing still on frictionless ice. They push on each other so that one person, of mass 120 kg, moves to the left at 2 m/s, while the other person, of mass 80 kg, moves to the right at 3 m/s. What is the velocity of their center of mass?

• Zero

• 0.5 m/s to the left

• 1 m/s to the right

• 2.4 m/s to the left

• 2.5 m/s to the right

A student conducts an experiment in which an object travels across a horizontal surface while for 2.0 s a net force is applied to a 2.0 kg object that initially travels with a speed of 0.5 m/s. Data collected from the experiment are used to create the graph of the magnitude of the applied force s exerted on the object as a function of time is shown. All frictional forces are considered to be negligible. Can the student use the graph and the known data to determine the momentum of the object after the force has been applied?

• Yes, because the average force exerted on the object can be used with the time interval of 2.0 s to determine the change in momentum of the object by using P=Ft

• Yes, because the area bound by the best-fit line and the horizontal axis from 0 to 2.0 s to can be used to determine the change in momentum of the object

• No, because the data is too scattered to determine the average force that is exerted on the object.

• No, because the student needs to know the direction that the force is applied to the object because the applied force will be in the same direction as the change in momentum of the object.

• Only equation 1, because the momentum lost by cart A is gained by cart B. This change in momentum can be determined using the graph

• Only equation 2, because the force is exerted only on cart B , so there is no information about the exerted on cart A.

• Equation 1 and equation 2, because the system is closed and all quantities are known except for the final speed of cart A.

• Neither equation, because there are too many unknown quantities

An object of mass 5.0 kg travels in the positive direction with a speed of 1.0 m/s. The object collides with a second object that exerts an average net force over an interval of time such that the 5.0 kg object comes to rest. Which of the following best predicts the change in momentum for the 5.0 kg object?

• The change in momentum is in the negative direction.

• The change in momentum is in the positive direction.

• The change in momentum is zero

• The direction of the change in momentum cannot be determined without knowing the value of the average force and time in which the force is exerted

Which of the following is true for both spheres?

• The maximum kinetic energy is attained as the sphere passes through its equilibrium position.

• The maximum kinetic energy is attained as the sphere reaches its point of release.

• The minimum gravitational potential energy is attained as the sphere passes through its equilibrium position.

• The maximum gravitational potential energy is attained when the sphere reaches its point of release.

• At x = 0, its velocity is zero.

• At x = 0, its acceleration is at a maximum.

• At x = A, its displacement is at a maximum

• At x = A, its velocity is at a maximum

• The potential energy of the spring is at a minimum at x = 0.

• The potential energy of the Spring is at a minimum at x = A

• The kinetic energy of the block is at a minimum at x =0

• The kinetic energy of the block is at a maximum at x = A

A pendulum consisting of a sphere suspended from a light string is oscillating with a small angle with respect to the vertical. The sphere is then replaced with a new sphere of the same size but greater density and is set into oscillation with the same angle. How do the period, maximum kinetic energy, and maximum acceleration of the new pendulum compare to those of the original pendulum?

• Period Larger; Max KE Larger; Max Acceleration Smaller

• Period Smaller; Max KE Larger; Max Acceleration Smaller

• Period same; Max KE same; Max Acceleration same

• Period same; Max KE Larger; Max Acceleration same