Question

A body falls from a height of $200$ m. If gravitational attraction ceases after $2$ s, further time taken by it to reach the ground is ($g=10m{s}^{-2}$)

• A. $5s$
• B. $9s$
• C. $13s$
• D. $17s$

Answer 1

Answer: (B)

$9s$

Distance travelled in $2sec$.
$s=ut+\frac{1}{2}g{t}^2=\frac{1}{2}g(2{)}^2=2g=20mt$

Remaining $=180m$
$v=u+gt=0+10\times 2=20m/s$

So, after this velocity will be constant (20 m/s) downwards (since no $g$ is acting)
Hence, time taken $=\frac{180}{20}=9sec$