Question

what will be the work done in raising the velocity of a car weighing 2000 kg from 18 km per hour to 54 km per hour

Answer 1

As we know that

Work done = Force × displacement
Force = Mass × acceleration

Now
Given that
Initial velocity(u) = 18 km/h or = 18 × 5/18
= 5 m/s

Final velocity(v) = 54 km/h or = 54 × 5/18
= 15 m/s

As time is not provided then Let time = 1 sec

Now
Acceleration = (v - u)/t
= (15 - 5)/1
= 10 m/s^2

Now
Displacement :-

S = ut + 1/2× a ×t^2
=> S = 5 × 1 + 1/2 × 10 × 1 × 1
=> S = 5 + 5
=> S = 10 meter

Now
Force :-

Mass = 2000
Acceleration = 10m/s^2

Then
Force = 2000 × 10
= 20000 Newton

Now
Work Done :-

Force = 20000 Newton
Displacement = 10 meter

=> W = 20000 × 10
=> W = 200000 Newton Meter
or W = 200000 Joules

Answer 2

Your answer is here ....

Mass of car = 2000 kg

Initial velocity (u) =>18 Km/h
=18*5/18
=5 m/s

Initial kinetic Energy = 1/2 mu²
=1/2*2000*5²
=1000*25
=25000 J

Final velocity (v) =>54 km/h
=54*5/18
=15 m/s

Final kinetic energy = 1/2 mv²
=1/2*2000*15²
=1000*225
=225000 J

Work Done = Change in kinetic energy
Work Done=225000J - 25000J
$\bold{Work\:Done=200000J}$

Hope it helps