Question

A particle moves in a straight line with velocity 20 $\frac{m}{s}$ and acceleration -4 $\frac{m}{s^2}$. Find the velocity after 5 seconds.

• A. $40\frac{m}{s}$
• B. $0$
• C. $20\frac{m}{s}$
• D. $-20\frac{m}{s}$

Answer 1

The correct option is B

$0$

Given, initial velocity, $u=20\frac{m}{s}$,

time taken $t=5s$ and

acceleration $a=-4\frac{m}{s^2}$

Final velocity $v=u+at$

$\Rightarrow v=20+(-4\times 5)$

$\Rightarrow v=0$

Since the acceleration is negative, the body is decelerating so it comes to rest after 5 seconds.