Question

A body falls from a height of 100m . After 2 seconds if gravity disappears, find the total time it would take to reach the ground.
​

Answer 1

${\huge{\boxed{\mathcal{\red{Answer}}}}}$

Time taken = 6secs

${\huge{\boxed{\mathcal{\red{Explanation}}}}}$

It is given that the gravity disappears after 2s. Thus after 2s body will travel with its final velocity.

Now the key words given are :

Initial velocity = 0m/s

Final velocity = ?

Distance to travel = 100m.

Gravity is till = 2secs.

Now, according to first equation of motion :

$v = u + at$

$v = 0 + 10 \times 2$

$= 20m \div {s}^{2}$

(g) is taken for just simplifying the calculation.

Thus we get final velocity of body is 20m/s.

Now the distance body traveled by body in this 2 sec is : by second equation of motion :

$s = ut + \frac{1}{2} a {t}^{2}$

$s = 0 + \frac{1}{2} \times 10 \times {2}^{2}$

$s = 20m$

Since it traveled 20m in first 2secs , this means that the left distance is 80m.

So now the data we get is :

Distance left = 80m

Final velocity = 20m/s.

Time = ?

$t = \frac{80}{20}$

$t = 4s$

Now it will take 4s to travel 80m and it took 2s to travel 20m, thus the total time taken to reach the earth

$= 2 + 4 = 6s$

______________________________________

BY √\_________ SCIVIBHANSHU

THANK YOU.

STAY CURIOUS