f4 physics question

2007-09-23 4:50 pm

a squash ball hits a wall perpendicularly at 17m/s and rebounds at 10m/s along its original path. if it takes 0.8s for the ball to rebound, what is the magnitude of the average acceleration of the ball?

回答 (1)

Audrey Hepburn

2007-09-23 4:59 pm

✔ 最佳答案

Take the direction when the ball travels to the wall be positive.

Initial velocity, u = 17 ms-1

Final velocity, v = -10 ms-1

Time taken, t = 0.8 s

By impulse = change of momentum

Ft = mv – mu

F(0.8) = m(-10 - 17)

F = -33.75m N

And by Newton’s 2nd law of motion,

F = ma

We can obtain:

ma = -33.75m

a = -33.75 ms-2

So, the magnitude of average acceleration is 33.75 ms-2.

2007-09-23 09:23:28 補充：
It is because the time taken by the ball to rebound is 0.8 s. Therefore, the impact time (the time when the ball experience the force) is 0.8 s.

參考: Myself~~~

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