Physics chapter 8

A 0.200-kg mass hangs from the end of a vertical spring causing it to stretch 5.0 cm. If another 0.200-kg mass is added to the spring, the potential energy of the spring will be

4 times

In which one of the following systems is there an increase in gravitational potential energy?

A child accidentally releases a helium-filled balloon and it flies upward toward the clouds.

Which of the following statements is true?

A conservative force permits a two-way conversion between kinetic and potential energies.

Complete the following statement: A force that acts on an object is said to be conservative if

All these

Block 1 and block 2 have the same mass, m, and are released from the top of two inclined planes of the same height making 30° and 60° angles with the horizontal direction, respectively. If the coefficient of friction is the same in both cases, which of the blocks is going faster when it reaches the bottom of its respective incline?

Block 2 is faster.

Two blocks of masses m1 and m2 are released from the top of two frictionless inclined planes of the same height making 30° and 60° angles with the horizontal direction, respectively. Which of the blocks is going faster when it reaches the bottom of its respective incline?

Both blocks have the same speed at the bottom

You and your friend want to go to the top of the Empire State Building. Your friend takes the elevator straight up. You decide to walk up the spiral stairway, taking longer to do so. Compare the gravitational potential energy (U) of you and your friend, after you both reach the top. Assume you have the same mass.

Both of you have the same amount of potential energy.

A mass is attached to one end of a string. The other end of the string is attached to a rigid support. The mass is released at A and swings in a vertical arc to points B, C, and D, as shown in Figure 8-3. Neglect air resistance.

C

Which of the following is false regarding energy?

Energy can be created

An acorn falls from a tree. Compare its kinetic energy K, to its potential energy U.

K increases and U decreases

Two identical balls are thrown vertically upward. The second ball is thrown with an initial speed that is twice that of the first ball. How does the maximum height of the two balls compare?

The maximum height of the second ball is four times that of the first ball.

Two objects are moving at equal speed along a level, frictionless surface. The second object has twice the mass of the first object. They both slide up the same frictionless incline plane. Which object rises to a greater height?

The two objects rise to the same height.

The total mechanical energy of a system

is constant, only if conservative forces act.

If the slope of the curve on a potential energy versus position graph is positive, what can we say about the force?

the force is negative