Question

A particle moves along a straight line on $y-$axis. The distance of the particle from $O$ varies with time and is given by : $y=20t-t^2$. The distance travelled by the particle before it momentarily comes to rest is:

• A. $200m$
• B. $100m$
• C. $50m$
• D. $150m$

Answer 1

The correct option is B $100m$

$y=20t-t^2$

On differentiation we get

$v=20-2t$

When the body comes to rest momentarily v=0

$20=2t$

$t=10secs$

Displacement in 10 secs

$y=20\times 10-{10}^2=200-100=100$m