Physics Test 2

A horizontal disk rotates about a vertical axis through its center. Point is midway between the center and the rim of the disk, and point is on the rim. If the disk turns with constant angular velocity, which of the following statements about it are true? (There may be more than one correct choice.)

-Q is moving twice as fast as P. -The linear acceleration of is twice as great as the linear acceleration of P

As you are leaving a building, the door opens outward. If the hinges on the door are on your right, what is the direction of the angular velocity of the door as you open it?

Down

A box of mass is pressed against (but is not attached to) an ideal spring of force constant and negligible mass, compressing the spring a distance x. After it is released, the box slides up a frictionless incline as shown in the figure and eventually stops. If we repeat this experiment but instead use a spring having force constant 2k

-the box will go up the incline twice as high as before. -just as it moves free of the spring, the kinetic energy of the box will be twice as great as before. -just as it moves free of the spring, the speed of the box will be times as great as before.

Which, if any, of the following three statements concerning the work done by a conservative force is NOT true? Select option "All of the above statements are true." if all three statements are true.

All of the statements are true -It can always be expressed as the difference between the initial and final values of a potential energy function. -It is independent of the path of the body and depends only on the starting and ending points. -When the starting and ending points are the same, the total work is zero.

Two identical balls are thrown directly upward, ball A at speed and ball B at speed 2 , and they feel no air resistance. Which statement about these balls is correct?

Ball B will go four times as high as ball because it had four times the initial kinetic energy.

In a collision between two objects having unequal masses, how does magnitude of the impulse imparted to the lighter object by the heavier one compare with the magnitude of the impulse imparted to the heavier object by the lighter one?

Both objects receive the same impulse.

There must be equal amounts of mass on both side of the center of mass of an object.

False

A dumbbellshaped object is composed by two equal masses,m , connected by a rod of negligible mass and length r. If I(1) is the moment of inertia of this object with respect to an axis passing through the center of the rod and perpendicular to it and I(2) is the moment of inertia with respect to an axis passing through one of the masses, it follows that

I(2)>I(1)

A small car has a headon collision with a large truck. Which of the following statements concerning the magnitude of the average force due to the collision is correct?

The small car and the truck experience the same average force

When a rigid body rotates about a fixed axis, all the points in the body have the same

angular acceleration.

A box of m mass is pressed against (but is not attached to) an ideal spring of force constant k and negligible mass, compressing the spring a distance x. After it is released, the box slides up a frictionless incline as shown in the figure and eventually stops. If we repeat this experiment but instead compress the spring a distance of 2x

just as it moves free of the spring, the box will be traveling twice as fast as before.

A ball drops some distance and loses 30 J of gravitational potential energy. Do NOT ignore air resistance. How much kinetic energy did the ball gain?

less than 30 J

On a smooth horizontal floor, an object slides into a spring which is attached to another mass that is initially stationary. When the spring is most compressed, both objects are moving at the same speed. Ignoring friction, what is conserved during this interaction?

momentum and mechanical energy

A ball drops some distance and gains 30 J of kinetic energy. Do NOT ignore air resistance. How much gravitational potential energy did the ball lose?

more than 30 J

A 1.0kg block and a 2.0kg block are pressed together on a horizontal frictionless surface with a compressed very light spring between them. They are not attached to the spring. After they are released and have both moved free of the spring

the lighter block will have more kinetic energy than the heavier block.

In an INELASTIC collision between two objects

the momentum of the system is conserved but the kinetic energy of the system is not conserved

When you ride a bicycle, in what direction is the angular velocity of the wheels?

To your left

When an object is solely under the influence of conservative forces, the sum of its kinetic and potential energies does not change

True

Is it possible for a system to have negative potential energy?

Yes, since the choice of the zero of potential energy is arbitrary.