Question

A particle of mass 2 kg moves with an initial velocity of $\overrightarrow{v}=4\hat{i}+4\hat{j}m{s}^{-1}$. A constant force of $\overrightarrow{F}=-20\hat{j}N$ is applies on the particle. Initially, the particle was at (0,0). The x-cordinate of the particle when its y-coordinate again becomes zero is given by

• A. 1.2 m
• B. 4.8 m
• C. 6.0 m
• D. 3.2 m

Answer 1

The correct option is D

3.2 m

$\overrightarrow{a}=\frac{\overrightarrow{F}}{m}=-10\hat{j}m{s}^{-2}$
$Displacementiny-direction$
$y=ut+\frac{1}{2}a{t}^2$
$\Rightarrow 0=4\times t\times -\frac{1}{2}\times 10\times t^2$
$t=\frac{4}{5}s\Rightarrow x=4t=4\times \frac{4}{5}=3.2m$