Question

If position of particle is changing with time as r = t² – 2t (m). Find the velocity at t = 2 second 

(1) 2 m/s 

(2) 3 m/s 

(3) 0 m/s 

(4) 4 m/s

Answer 1

Correct option is (1) 2 m/s 

Answer 2

r=t²  -2t(m)

Differentiating wrt t,

dr/dt=dt²/dt-2dt/dt                     [dr/dt=v]

v=2t-2

v at t=2,

v=2(2)-2

v=2 m/s