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  • A body of mass 5kg is acted upon by a force F =(-3i +4j)N

A body of mass 5kg is acted upon by a force F= (-3\widehat{i}+4\widehat{j})N. If its initial velocity at t=0 is v= (6\widehat{i}-12\widehat{j})ms^{-1}, the time at which it will just have velocity along the y-axis is

(a) never
(b) 10 s
(c) 2 s
(d) 15 s

Answers (1)

The answer is the option (b) 10s

Explanation:

Initial velocity (u) = (6\widehat{i} + 12\widehat{j}) ms^{-1}

Force, F= (-3\widehat{i}+4\widehat{j})N, Mass (m) = 5kg

\overrightarrow{a} = \frac{\overrightarrow{F}}{m} = (\frac{-3}{5}\widehat{i}+ \frac{4}{5}\widehat{j}) ms^{-2}

Since there is only Y component in final velocity and the X component is zero,

v_{x} = u_{x} + a_{x}t

0 = 6 + \frac{-3}{5} t \rightarrow \frac{3}{5}t = 6

t = 10s.

Posted by

infoexpert24

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