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You throw a baseball 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) The work is positive on the way up and positive on the way down. B) The work is positive on the way up and negative on the way down. C) The work is negative on the way up and positive on the way down. D) The work is negative on the way up and on the way down because gravity is always

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Answer:

C) The work is negative on the way up and positive on the way down.

Explanation:

The general formula for the work done on an object is given as follows:

W = F d Cosθ

where,

W = Work Done

F = force applied

d = displacement covered

θ = angle between direction of motion force

So, when the baseball goes up, the gravitational force acts upon it in downward direction. And the motion of the ball is in upward direction. So, the motion and force are both in opposite directions. This means θ = 180°. Hence,

(W)up = F d Cos 180° = F d(-1)

(W)up = - F d

Thus, the work done on baseball during upward motion is negative

Now, when the baseball goes down, the gravitational force acts upon it in downward direction. And the motion of the ball is also in downward direction. So, the motion and force are both in same directions. This means θ = 90°. Hence,

(W)up = F d Cos 90° = F d(1)

(W)up = F d

Thus, the work done on baseball during downward motion is positive

So, the correct option is:

C) The work is negative on the way up and positive on the way down.

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