Question

A body of mass $5kg$ starts motion form the origin with an initial velocity $\overrightarrow{u}=(30\hat{i}+40\hat{j})m{s}^{-1}$ If a constant force $\overrightarrow{F}=-(\widehat{-6i}-5\hat{j})N$ acts on the body, than the time in which the Y-component of the velocity becomes zero is ________

• A. $5s$
• B. $20s$
• C. $40s$
• D. $80s$

Answer 1

Answer: (C)

$40s$

Acceleration is $y=-1$

Initial $yvelocity=40$

Therefore $v=u-at$

$v=0:u=at40=\left(1\right)\left(t\right)\Rightarrow t=40seconds$