Question

You throw a ball straight up. Compare the sign of the work done by gravity while the ball goes up with the sign of the work done by gravity while it goes down.

a. Work is + on the way up and + on the way down
b. Work is + on the way up and - on the way down
c. Work is - on the way up and + on the way down
d. Work is - on the way up and - on the way down

Answer 1

c. Work is - on the way up and + on the way down

Step-by-step explanation:

Work done is given as the product of the applied force and the displacement of the object.

Work done = F x d

Work done = mg x d

where;

g is acceleration due to gravity = 9.8 m/s²

When the ball goes up, it moves against the force of gravity which tends to pull every object downwards. Since the ball moves against gravity, the work done is negative.

Also, when the ball goes down, it moves in the direction of gravity which acts downwards. Since the ball moves in the same direction as gravity, the work done is positive.

The correct option is "C. Work is negative (-) on the way up and positive (+) on the way down"