Question

If an object with a mass of `5 kg` changes speed from `12m/s` to `8m/s`, by how much does its kinetic energy change?

Answer 1

`Delta E_k=-200 J`

Explanation:

`"data :"`
`m=5" kg 'mass of object'"`
`v_i=12" m/s ' initial velocity of object'"`
`v_l=8" m/s 'final velocity of object'"`
`E_k=1/2*m*v^2" The kinetic energy of object"`

`E_i=1/2*5*12^2`

`E_i=(5*144)/2`

`E_i=360 " J the initial kinetic energy of object"`

`E_f=1/2*5*8^2`

`E_f=5*64/2`

`E_f=160 " J the final kinetic energy of object"`

`Delta E_k=E_f-E_i`

`Delta E_k=160-360`

`Delta E_k=-200 J`