Question

a body of mass 500g with moving a speed 20m/s. a force act on it which make is to move with a speed 30m/s. the kinrtic energy of the body&work done by the force on the body.

Answer 1

m = 500 g = 0.5 kg

v_1 = 20 ms^(-1)

v_2 = 30 ms^(-1)

Let's find the kinetic energy in each case.

K_1 = m · (v_1)² / 2 = 0.5 × 20² / 2 = 100 J

K_2 = m · (v_2)² / 2 = 0.5 × 30² / 2 = 225 J

We know,

W = ∆K = K_2 - K_1

So,

W = (225 - 100)J = 125 J