Question

The speed of a car of mass 500kg increases from 72km/hr to 108km/hr. Calculate the work done in kJ

Answer 1

$\huge{\underline{\sf{\purpul{Answer-}}}}$

125000 KJ

Explanation:

work done = W = Final K.E. - Initial K.E.

so we will find the change in K.E which is = $\dfrac {1}{2} m(v^{2} _f - v^{2} _i)$

where m is mass of vehicle, $v_f$ is final speed and $v_i$ is initial speed.

we have,

$v_i = 72 km/h = 72\times (5/18) = 20 m/s$

$v_f = 108 \times (5/18) = 30 m/s$

by using this formula of change in K.E. $\dfrac {1}{2} m(v^{2} _f - v^{2} _i)$

we get $\dfrac {1}{2}\times 500 ( {30}^2- {20^2})$

so total work done = 125000 KJ