Question
A physics teacher throws a 4kg dodgeball 17m/s hitting a 58kg student,who is initially at rest on a skateboard. After hitting the student, the dodgeball rebounds back left with a speed of 5m/s vert Jvert =square unit before collision: Pball=square unit P_(student)=square unit after collision: Pball=square unit P_(student)=square unit v How fast did the student move after the impact? square square v What was the magnitude of the average impact force if the impact lasted 028s?
Solution
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Aurora
Veteran ยท Tutor for 12 years
Answer
To solve this problem, we need to apply the principles of conservation of momentum and impulse.### Before Collision:1. **Momentum of the dodgeball (P_ball):**
2. **Momentum of the student (P_student):** Since the student is initially at rest:
### After Collision:1. **Momentum of the dodgeball after rebounding:** The dodgeball rebounds with a speed of
in the opposite direction, so its velocity is
:
2. **Conservation of Momentum:** The total momentum before the collision equals the total momentum after the collision:
Solving for
:
3. **Velocity of the student after impact:**
### Impulse and Average Impact Force:1. **Impulse (J):** Impulse is the change in momentum of the dodgeball:
The magnitude of the impulse is:
2. **Average Impact Force (F_avg):** Using the impulse-momentum theorem, where impulse equals the average force times the time duration (
):
### Summary:- Magnitude of impulse:
- Velocity of the student after impact:
- Magnitude of the average impact force: