A body of mass 2 kg moving on a horizontal surface with an initial velocity of 4 m s- 1 comes to rest after 2 s . If one wants to keep this body moving on the same surface with a velocity of 4 m s- 1 the force required is

Question

A body of mass 2 kg moving on a horizontal surface with an initial velocity of 4 m s- 1 comes to rest after 2 s . If one wants to keep this body moving on the same surface with a velocity of 4 m s- 1 the force required is (A) 8 N (B) 4 N (C) Zero (D) 2 N

Tardigrade Admin · Accepted Answer

u=4m / s , v=0, t=2 sec v=u+at ⇒ 0=4+2a ⇒ a=-2m / s2 ∴ Retarding force=ma=2× 2=4 N This force opposes the motion. If the same amount of force is applied in forward direction, then the body will move with constant velocity.

Q. A body of mass $2 k g$ moving on a horizontal surface with an initial velocity of $4 m s^{- 1}$ comes to rest after $2 s$ . If one wants to keep this body moving on the same surface with a velocity of $4 m s^{- 1}$ the force required is

$8 N$

$4 N$

Zero

$2 N$

$u = 4 m / s, v = 0, t = 2 sec$
$v = u + a t \Rightarrow 0 = 4 + 2 a \Rightarrow a = - 2 m / s^{2}$
$∴$ $R e t a r d in g f orce = ma = 2 \times 2 = 4 N$
This force opposes the motion. If the same amount of force is applied in forward direction, then the body will move with constant velocity.

Q. A body of mass 2kg moving on a horizontal surface with an initial velocity of 4ms−1 comes to rest after 2s . If one wants to keep this body moving on the same surface with a velocity of 4ms−1 the force required is

8N

4N