Question

If an object with a mass of `2 kg` changes speed from `3 m/s` to `m/s`, by how much does its kinetic energy change?

Answer 1

`4J`

Explanation:

Recall that the formula for kinetic energy is:

`color(blue)(|bar(ul(color(white)(a/a)DeltaE_k=1/2mv^2color(white)(a/a)|)))`

where:
`DeltaE_k=`change in kinetic energy
`m=`mass (kilograms)
`v=`velocity (metres per second)

Start by breaking down `DeltaE_k` into final kinetic energy minus the initial kinetic energy.

`DeltaE_k=1/2mv_f^2-1/2mv_i^2`

Simplify.

`DeltaE_k=1/2m(v_f-v_i)^2`

Substitute the given values.

`DeltaE_k=1/2(2kg)(1m/s-3m/s)^2`

Solve.

`DeltaE_k=1/2(2kg)(4m^2/s^2)`

`DeltaE_k=color(green)(|bar(ul(color(white)(a/a)color(black)(4J)color(white)(a/a)|)))`