Laws Of Motion Question 172
Question: A body of mass 2 kg moving on a horizontal surface with an initial velocity of 4 m/sec comes to rest after 2 sec. If one wants to keep this body moving on the same surface with a velocity of 4 m/sec, the force required is[NCERT 1977]
Options:
A) 8 N
B) 4 N
C) Zero
D) 2 N
Show Answer
Answer:
Correct Answer: B
Solution:
$ u=4\ m/s $ , $ v=0,\ t=2\sec $
$ v=u+at $
therefore $ 0=4+2a $
therefore $ a=-2m/s^{2} $
$ \therefore $ Retarding force$ =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.
