Question

Answer questions 1-3 below, answer in SI units and include the (+/-) sign, please show work

1) Caesar drops a 3.9kg ball from a height of 4.2m. What is the work done by the force of gravity on the ball?

2) Caesar drops a 4.1kg ball from a height of 5.3m. What is the change in the gravitational potential energy?

3)Suppose you throw a ball upwards, and as you watch its trajectory, you wonder about the gravitational potential energy -- how does it change with the rise and fall of the ball? (In a and b choose one of the answer choices provided)

a) on the way up: gravitational potential energy increases or gravitational potential energy decreases or there is no change is gravitational potential energy

b) on the way down: gravitational potential energy increases or gravitational potential energy decreases or there is no change is gravitational potential energy

Answer 1

1 . Here work done by gravity will be given as,

Wg = mgh = 3 9 × 9.8 × 4.2 = 160.524 J

Note work done by gravity is negative only when body moes upward.

2. Change in gravitational potential energy will be given as,

Here when object at height 5.3 m then body has the potential energy as Ui = mgh

When body reach the ground then potential energy will be zero so that,

Delta U = Ui-Uf = -mgh = - 4.1×9.8×5.3 = ( - 212.954) J

3.

a) on the way up: gravitational potential energy increases

Because E = mgh so as the height increases gravitational potential energy increases

b) on the way down: gravitational potential energy decreases

Because E = mgh so as h decreasing gravitational potential energy decreases.