Question

A particle starts to move in a straight line from a point with velocity $10m{s}^{-1}$ and acceleration $-2.0m{s}^{-2}$. Find position(S) and velocity(v) of the particle at $t=5$ s

• A. $S=25m,v=0m/s$
• B. $S=-25m,v=0m/s$
• C. $S=5m,v=10m/s$
• D. $S=0m,v=0m/s$

Answer 1

The correct option is A $S=25m,v=0m/s$

Displacement at $t=5s$ is

$S=ut+\frac{1}{2}a{t}^2$

$=10\times 5+\frac{1}{2}\times (-2.0)\times (5{)}^2$

$=50-25=25m$

i.e., after $5s$, the particle will be at distance $25m$ from the starting point.

Velocity at $t=5s$ is

$v=u+at$

or $v=10+(-2)\times 5=0$