A 1.0 kg ball moving at 2.0m/s perpendicular to a wall rebounds from the wall at 1.5m/s. The change in the momentum of the ball is:
Correct answer: D. 3.5 N s away from the wall
- A. Zero
- B. 0.5 N s toward the wall
- C. 0.5 N s away from the wall
- D. 3.5 N s away from the wall
Explanation
The initial momentum (Pi) of the ball is calculated as mvi = (1 kg)(2 m/s) = 2 N s towards the wall. After rebounding, the final momentum (Pr) is mvf = (1 kg)(-1.5 m/s) = -1.5 N s away from the wall. The change in momentum (△P) is calculated as Pr - Pi = -1.5 N s - 2 N s = -3.5 N s. Since momentum is a vector quantity, the magnitude of the change is 3.5 N s directed away from the wall.Option A is incorrect because the change in direction upon rebounding means the momentum changes. Option B is incorrect as it suggests a change toward the wall, but the ball actually moves away. Option C is incorrect because it underestimates the magnitude of the momentum change.
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