Question

The velocity of a car increase from
54 km/hr to 72 km/hr. How much is
the work done if the mass of the car
is 1500 kg ?​

Answer 1

Answer :-

W = 131.25 KJ

Given :-

u = 54 km/hr

= 54 × 5/18

= 3 × 5

= 15 m/s

v = 72 km/hr

= 72 × 5/18

= 4 × 5

= 20 m/s

m = 1500 kg

To find :-

The work done.

Solution:-

The work done by the car is equal to the change in the kinetic energy.

Kinetic energy is given by :-

$\huge \boxed{K_e = \dfrac{1}{2}mv^2}$

Now,

→$W = \dfrac{1}{2}mv^2 - \dfrac{1}{2}mu^2$

→$W = \dfrac{1}{2}m (v^2 - u^2 )$

Put the given values,

→$W = \dfrac{1}{2}\times 1500[(20)^2 - (15)^2 ]$

→$W = \dfrac{1}{2} \times 1500 ( 400 - 225 )$

→$W = \dfrac{1}{2} \times 1500 \times 175$

→$W = 750 \times 175$

→$W = 131,250 J$

Divide it by 1000

→$W = \dfrac{131,250}{1000}$

→$W = 131.25 KJ$

hence,

The work done is 131.25 KJ.