Question

If a `2 kg` object is constantly accelerated from `0m/s` to `18 m/s` over `5 s`, how much power musy be applied at `t= 2`?

Answer 1

We use the relation `P=Fv` to show that the power applied at `t=2s` is 51.8 watts.

Explanation:

First, we find the acceleration of the object

`a=(Deltav)/(Deltat)=18(m/s)/(5s) = 3.6m/s^2`

This means the net force on the object is

`F=ma = (2kg)(3.6m/s^2) = 7.2 N`

To calculate power, we use the relation

`P=Fv`

To determine the velocity at `t=2s`, use an equation of motion

`v_f=v_i + a(Deltat)`

`v_f=0 + (3.6m/s^2)(2s) = 7.2 m/s`

Therefore the power applied at `t=2s` is

`P=Fv=(7.2N)(7.2m/s)=51.8 W`