A football player kicks a ball forward. Later, a goalkeeper catches the ball and brings it to rest. Which of the following statements are correct? 1. The player does positive work on the ball. 2. The goalkeeper does negative work on the ball. 3. During the kick, force and displacement are in the same direction. 4. During the catch, force and displacement are in opposite directions.
1, 2, 3 and 4
Work done by a force is positive when the force and the displacement it produces act in the same direction, and negative when they act in opposite directions.
When the player kicks the ball forward, the force applied and the resulting displacement of the ball are in the same direction, so the player does positive work on the ball, making statements 1 and 3 correct.
When the goalkeeper catches the ball and brings it to rest, the force applied by the goalkeeper acts opposite to the ball's motion to decelerate it, so the force and displacement are in opposite directions and negative work is done, making statements 2 and 4 correct.
Hence, the correct answer is 1, 2, 3 and 4.
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