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JAMB Physics 1988 Question 7

Question 7

Newton's Laws and Momentum

When taking a penalty kick, a footballer applies a force of 30.0 N for a period of 0.05 s. If the mass of the ball is 0.075 kg, calculate the speed with which the ball moves off.

  1. A.4.50 m s−1
  2. B.11.25 m s−1
  3. C.20.00 m s−1
  4. D.45.00 m s−1.
Show the answer and explanation

Answer: C (20.00 m s−1)

Explanation

Impulse = change in momentum: 30 × 0.05 = 0.075 × v, so v = 1.5/0.075 = 20 m s−1.