Question

A ball is thrown upwards with a speed of $50m/s$. Find the distance travelled by the ball in last $2s$ of its ascent. (Take $10m/s^2$)

• A. $35m$
• B. $10m$
• C. $20m$
• D. $5m$

Answer 1

The correct option is C $20m$

Initial velocity $-50m/s$(opposite to the direction of acceleration)

Final velocity$=10m/s$ (completing the ascent)

Time taken $=\frac{0-(-50)}{acceleration}=\frac{50}{10}=5s$

$S_{th}=$Initial acceleration +$\frac{1}{2}$acceleration ($2\times$ (time)-1)

$S_{4th}=-50+\frac{1}{2}\times 10\left(7\right)=-15m$

$S_{5th}=-50+\frac{1}{2}\times 10\left(9\right)=-5m$

$S_{4th}+S_{5th}=-20m$(Negative as it is opposite to direction of acceleration)