A ball of mass 0.2 kg is thrown vertically upwards by applying a force by hand. If the hand moves 0.2 m while applying the force and the ball goes up to 2 in height further, find the magnitude of the force. Consider g = 10m/s 2
Correct answer: A. 22N
- A. 22N
- B. 16N
- C. 20N
- D. 4N
Explanation
The hand does work equal to the ball's gain in gravitational potential energy while it moves 0.2 m and then rises a further 2.0 m: F x 0.2 m = mg x 2.2 m = 0.2 kg x 10 m/s² x 2.2 m = 4.4 J. Therefore F = 4.4 J / 0.2 m = 22 N. A student may choose 20 N by ignoring the 0.2 m rise while the hand is still applying the force.
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