Question

If an object with a mass of `5 kg` changes speed from `5m/s` to `10 m/s`, by how much does its kinetic energy change?

Answer 1

The object has gained `375 \ "J"` of kinetic energy.

Explanation:

The initial kinetic energy is:

`"KE"_1=mv_1^2`

• `m` is the mass of the object in kilograms

• `v_1` is the initial velocity, which is `5 \ "m/s"`.

And so, we get,

`"KE"_1=5 \ "kg"*(5 \ "m/s")^2`

`=5 \ "kg"*25 \ "m"^2"/s"^2`

`=125 \ "J"`

The final kinetic energy is:

`"KE"_2=mv_2^2`

• `v_2` is the final velocity, which is `10 \ "m/s"`.

Again, we just plug in values into the equation, and we get,

`"KE"_2=5 \ "kg"*(10 \ "m/s")^2`

`=5 \ "kg"*100 \ "m"^2"/s"^2`

`=500 \ "J"`

The change in kinetic energy is:

`Delta"KE"="KE"_2-"KE"_1`

`=500 \ "J"-125 \ "J"`

`=375 \ "J"`