Question

If a `12 kg` object is constantly accelerated from `0m/s` to `60 m/s` over 8 s, how much power musy be applied at `t=3`?

Answer 1

The power is `=2025W`

Explanation:

The mass of the object is `m=12kg`

The initial velocity is `u=0ms^-1`

The final velocity is `v=60ms^-1`

The time is `t=8s`

Apply the equation of motion

`v=u+at`

To calculate the acceleration

`a=(v-u)/t=(60-0)/8=7.5ms^-1`

According to Newton's Second Law

`F=ma`

The force is

`F=12*7.5=90N`

The velocity when `t=3` is given by the equation

`v=u+at=0+3*7.5=22.5ms^-1`

The power is

`P=Fv=90*22.5=2025W`