- #1

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A person on a trampoline bounces straight upward with an initial speed of 4.0 m/s.

What is the person's speed when she returns to her initial height?

The answer is 4.0 m/s.

Can you guys explain why though?

Thanks so much!

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- Thread starter revernance
- Start date

- #1

- 1

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A person on a trampoline bounces straight upward with an initial speed of 4.0 m/s.

What is the person's speed when she returns to her initial height?

The answer is 4.0 m/s.

Can you guys explain why though?

Thanks so much!

- #2

arildno

Science Advisor

Homework Helper

Gold Member

Dearly Missed

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At the top, all kinetic energy had been converted into potential energy; returning, that potential energy re-converted into kinetic energy.

- #3

Doc Al

Mentor

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Hint: It's got nothing to do with trampolines. If you threw a rock straight up into the air with a speed of 4 m/s, what speed will it have when it falls back into your hand? (Ignoring air resistance, of course.)

- #4

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Also don't forget the difference between velocity and speed. Initial speed = final speed, sure. But initial velocity, +4.0 m/s in the y-axis (for trampoline example) yields -4.0m/s in the y-axis for final velocity.

- #5

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when u throw the body and it reaches the max height, its velocity is 0( so KE is 0), whereas it has PE( which is = to mgh)

when it reaches back to the point of projection, its KE will be equal to the PE at highest point( since gravity is conservative force). therefore , the velocity will be equal to the velocity with which u throw...

- #6

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initial velocity = u

at highest point v=0;

v=u+at;

a=g=10 m/s^2

u=10t;

now from highest point.

u=0;

v=0-10t(- ve for direction);

v= -10t;

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