3. A piece of fruit falls straight down. As it falls, A. the gravitational force

Question

3. A piece of fruit falls straight down. As it falls, A. the gravitational force does positive work on it and the gravitational potential energy decreases. B. the gravitational force does positive work on it and the gravitational potential energy increases. C. the gravitational force does negative work on it and the gravitational potential energy increases. D. the gravitational force does negative work on it and the gravitational potential energy decreases. Three blocks are connected as shown. The ropes and pulleys are of negligible mass. When released, block C moves downward, block B moves up the ramp, and block A moves to the right. After each block has moved a distance d, the force of gravity has done A. positive work on A, B, and C. B. zero work on A, positive work on B, and negative work on C. C. zero work on A, negative work on B, and positive work on C. D. none of these In order to catch a ball, a baseball player moves his or her hand backward in the direction of the all's motion. Doing this reduces the force of impact on the player's hand principally because it increases the impact time. decreases the impulse on the glove. decreases the change in momentum of the ball. all of the above one of the above

Explanation / Answer

Gravitational force = weight of the body, which acts vertically downwards.

So, if the diplacement is downward, gravitational work is positive. If displacement is upwards, it is negative. If there is no vertical displacement, it is zero.

Gravitattional PE is a measure of height. It increases with increase in height and vice versa.

Knowing this much will hopefully let us understand and solve the following questions, 3 and 4.

3) Ans: (a)

4) Ans: (c)

5) Ans: (d) All of the above.

Firstly it decreases the impact time.

Impulse I = Ft, so as t decreases, I alse decreases.

By impulse mpmentum theorem, change in momentum = I, so it also decreases.

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