Question

An object of 40 kg mass is moving with velocity 2 m/s. A force applied on it increases its velocity to 5m/s. Find the work done by force.

Answer 1

As work done ∆W=force ×distance

Answer 2

The work done by the force is equal to 420J.

Force on the 40 kg mass , F = mass ×acceleration

F = ma = 40a

Using the equation of motion to find the distance travelled by the mass , v² - u² = 2as

s - distance travelled

v - final velocity of the mass = 5 m/s

u - initial velocity of the mass = 2 m/s

s = (v²-u²)/2a = (25-4)/2a = 21/2a

Work done by the force = force × distance travelled by the mass

= 40a × 21/2a

= 420 J