Laws Of Motion Question 259

Question: A body of mass 5 kg starts from the origin with an initial velocity $ \overrightarrow{u}=30\hat{i}+40\hat{j}m{{s}^{-1}} $ . If a constant force $ \overrightarrow{F}=-(\hat{i}+5\hat{j})N $ acts on the body, the time in which the y?component of the velocity becomes zero is [EAMCET (Med.) 2000]

Options:

A) 5 seconds

B) 20 seconds

C) 40 seconds

D) 80 seconds

Show Answer

Answer:

Correct Answer: C

Solution:

$ u _{y}=40m/s $ , $ F _{y}=-5N $ , $ m=5kg $ .

So $ a _{y}=\frac{F _{y}}{m}=-1m/s^{2} $

(As $ v=u+at $ ) \ $ v _{y}=40-1\times t=0 $

therefore $ t=40\sec $ .



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