Question

A boy jumps vertically upwards fromthe top of a platform and then drops onto a trampoline which is 3m below his start point.

If the trampoline has an effective spring constant 5.2x10^4N/m and is depressed 0.35m, calculate the boy's initia; upward velocity.

Answer 1

The initial velocity will depends on the mass of boy.

Answer 2

You are given the spring constant and the intial displacement of the trampoline. You can use these to determine the spring potential in order to find the energy at the point when the boy makes contact with the trampoline. Just work backwards and use the law of energy conservation in order to cancel out the masses.

Answer 3

let initial velocity be v.

then initial energy=0.5*m*v^2(assume potential energy at this height is 0.then if we go up,potnetial energy will increase and if we go down,energy will decrease.)

so as spring is depressed, total depth=3.35 m

so at this depth,total energy=-m*g*3.35+0.5*5.2*10^4*0.35^2

so equating this energy with initial kinetic energy,

we get

v=79.4 m/s

Answer 4

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