Figure shows the position-time graph of a particle of mass 4 kg. What is the (a) force on the particle for t < 0, t > 4 s, 0 < t < 4 s? (b) impulse at t = 0 and t = 4 s ? (Consider one-dimensional motion only).

Explanation

(a) For t < 0. No force as Particles is at rest.
For > 4s, No force again particle comes at rest.
For 0 < t < 4s, as slope of OA is constant so velocity constant i.e., a = 0, so force must be zero .
(b) Impulse at t= 0
Impulse = change in momentum
`I = m (v -u) = 4(0 - 0.75) = 3kg ms^(-1)`
Impulse at t = 4s
`I = m(v - u) = 4 (0 - 0.75) = - 3kgms^(-1)`