Question

If a 75-kg runner can accelerate from standing start to a speed of 10m/s in 3 seconds, ho much power is generated?

I'll just check my answer, please show your solutions. :)

Answer 1

1250

Answer 2

y 1250???

Answer 3

yap 1250

Answer 4

We can calculate the kinetic energy of the runner after 3 seconds:
Ekin = 0.5m.v² = 3750 Joule
Power = dW/dt (power is work done per unit of time)
The runners initial kinetic energy was zero , therefore is Ekin = W
P = dW/dt = Ekin/t = 3750J/3s = 1250 Watt. (this is not instantaneous power but mean power <P>)

<P>= W/dt (dt is specified time interval)

It seems that runners can generate so much power but only for a short time. Once the velocity is build up, the maintenance power needed is much less. Unless the runner crashes and gives all the power back to Mother earth.