Question

If a `2 kg` object is constantly accelerated from `0m/s` to `15 m/s` over `12s`, how much power musy be applied at `t= 9`?

Answer 1

The power is `=28.125W`

Explanation:

The mass of the object is `m=2kg`

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

The final velocity is `v=15ms^-1`

The time is `t=12s`

Apply the equation of motion

`v=u+at`

The acceleration is

`a=(v-u)/t=(15-0)/12=1.25ms^-2`

Acording to Newton's Second Law of Motion

`F=ma`

The force is

`F=2*1.25=2.5N`

When `t=9`, the velocity is

`v_9=0+1.25*9=11.25ms^-1`

The power is

`P=Fv=2.5*11.25=28.125W`