A particle of mass 2.5 kg is moving at a speed of 12 m/s. If a force of magnitude 10 N acts against it, find how long it takes to come to rest.
-
A.
1.5 s -
B.
3.0 s -
C.
4.0 s -
D.
6.0 s
Correct Answer: Option B
Explanation
(F = ma )
(10 = 2.5a implies a = 4 ms^{-2})
Since it is a retarding movement, then (a = -4 ms^{-2}).
(v = u + at; v = 0 ms^{-1}, u = 12 ms^{-1})
(0 = 12 + (-4t) implies 0 = 12 – 4t)
(4t = 12 implies t = 3 s)