4.3.1 Work and Gravitational Potential Energy

Question 1

Work and Gravitational Potential Energy

Answer 1

• The gravitational potential energy of an object due to its distance (y) from the Earth’s surface is .
• Because the coordinate system you choose may influence the value of y, it is preferable to calculate the change in gravitational potential energy, .

Question 2

After an object that falls from a height h hits a surface and comes to rest, what happens to its energy?

Answer 2

It is converted into thermal energy.

Question 3

Which of the following statements about gravitational potential energy is not true?

Answer 3

It is equal to the kinetic energy of the falling object at y = 0.

Question 4

Consider two objects, object a with a mass m and object b with a mass 2m, are lifted to the same height and released. Which of the following relates to their velocities as they hit the surface?

Answer 4

vb = va

Question 5

How much work is required to lift a 2 kg ball 3.5 m vertically from its starting point?

Answer 5

68.6 J

Question 6

Tow objects at rest with the same mass are dropped from two different heights, h1 and h2, where h1 = 2h2. Which of the following correctly relates their final velocities?

Answer 6

v1 = sqrt(2)v2

Question 7

If an object is shot straight up in the air with a velocity of 5 m / s, how high will it go?

Answer 7

1.3 m

Question 8

How much work does gravity do as a 2 kg ball is lifted 3.5 m above its starting point?

Answer 8

−68.6 J

Question 9

As a climber scales a mountain, his potential energy increases but his kinetic energy doesn’t change. Where does this extra energy come from?

Answer 9

his muscles