Certain force acting on a 20 kg mass changes its velocity from `5m//s to 2m//s`. calculate the work done by the force.

Answer

210 J

Explanation

Kinetic energy is given by the expression `(E_(k))_(v)=1//2 mv^(2)`
Where,
`E_(k)` = Kinetic energy of the object moving with a velocity, v
(i) Kinetic energy when the object was moving with velocity `5 ms^(-1)`
`(E_(k))_(5)=1//2 xx 20 (5)^(2) = 250 J`
Kinetic energy when the object was moving with a velocity `2 ms^(-1)`
`(E_(k))_(2) = 1//2 xx 20 xx (2)^(2) = 40 J`.