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# Energy watch

1. A pole vaulter has a weight of 500N.
a) she vaults to a height of 4m. How much work does she do.
I have F= W/D so F is 500J
B) how much kinetic energy does she have just before she lands?
C) when she lands, her trainers compress by 1cm. Calculate the average force acting on her trainers as she is landing.
If anyone could help with the bottom two questions that would be greatly appreciated please
2. (Original post by Deborahmich)
A pole vaulter has a weight of 500N.
a) she vaults to a height of 4m. How much work does she do.
I have F= W/D so F is 500J
B) how much kinetic energy does she have just before she lands?
C) when she lands, her trainers compress by 1cm. Calculate the average force acting on her trainers as she is landing.
If anyone could help with the bottom two questions that would be greatly appreciated please
For B), use gravitational potential energy (E = mgh). This must all be converted to kinetic energy at the instant before she lands.

For C), use the KE equation (KE = mv2/2) rearranged to give velocity as the subject.

Then find the deceleration from that velocity to 0 in the distance of 1cm.

Finally use F = ma.

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