Question

A balloon is going upwards with velocity 12 m/s. It releases a packet when it is a height of 65 m from the ground. How much time will the packet take to reach the ground if g = 10 $m/s^2$

• A. 5 second
• B. 6 second
• C. 7 second
• D. 8 second

Answer 1

The correct option is A 5 second

Given,

Take upward direction as -ve and downward direction as +ve.

$u=-12m/s$

$h=65m$

$g=10m/s^2$

$v=0m/s$

From 2nd equation of motion,

$h=ut+\frac{1}{2}g{t}^2$

$65=-12t+\frac{1}{2}\times 10t^2$

$65=-12t+5t^2$

$5t^2-12t-65=0$

$5t(t-5)+13(t-5)=0$

$t-5=0,5t+13=0$

$t=-\frac{13}{5},5$

Time taken to reach the ground is $5sec$.

The correct option is A.