Question

A pebble is thrown vertically upwards with a speed of $20m{s}^{-1}$. How high will it be after $2s$? (Take $g=10m{s}^{-2}$)

• A. 40 m
• B. 10 m
• C. 20 m
• D. 25 m

Answer 1

The correct option is C 20 m

Initial velocity , $u=20m/s$
Since, the ball is thrown upward, so 2nd equation of motion will be given by,
$S=ut-\frac{1}{2}g{t}^2$
$\Rightarrow S=20\times 2-\frac{1}{2}\times 10\times 2^2=40-20=20m$