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twilight:
welcumzz ;)

emi:
another Q ..
how do we calculate energy stored ?

here is a Question :

A bungee jumper of mass 60kg jumps from a bridge tied to an elastic rope which becomes taut after he falls 10m. Consider the jumper when he has fallen another 10m and is traveling at 15m/s

a) work out how much energy us stored in the rope, take g=10 m/s2 and ignore air resistance .


plz some one help me out

twilight:
i think its this way.

if u consider the mechanical energies( gravitational potential energy, elastic potential energy, kinetic energy)
total mechanical energy at the moment he jumps = total mechanical energy when he has fallen 20 m
             KE    +    EPE   +     GPE                      =        KE              +    EPE       +     GPE
             0     +      0    +     mxgxh                    =      1/2 mv2          +    EPE       +      0
                                      60 x 10 x 20              =    0.5 x 60 x 152    +   EPE
                                           12000                  =        6750              +   EPE

therefore     EPE( i.e. energy stored in the rope)   =        12000 - 6750         =         5250 J

emi:
Thanks i didn't think of that

twilight:
welcumzz .. r sure this is IGCSE ??
bcoz i studied this in mechanics A level

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