A cricket ball of mass 0.16 kg comes at 28 m/s and is caught.
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
A cricket ball of mass comes at and is caught. What is the average force on the fielder's hands if the ball is stopped in
- , with stiff hands;
- , when the fielder pulls the hands back?
Need a reminder? The key ideaShow
Momentum is , a vector. A force acting for a time changes it. The change is the impulse:
Choose a positive direction and give every velocity its sign. For a force that changes with time, the impulse is the area under the force-time graph.
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Given. , , .
Plan. The hands must remove the same momentum either way. A longer time means a smaller force.
Step 1. Momentum to remove. .
Step 2. Stiff hands. .
Step 3. Pulling back. .
Answer: (a) . (b) , about twelve times less.
Check. The time grew by times, and the force fell by the same factor. Good.
Watch out. Pulling the hands back does not reduce the impulse. It only spreads it over a longer time.
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