Question

A body is allowed to fall from a height of 100 m. After 2 seconds if acceleration due to raviny
vanishes, the total time of its fall is (g = 10 ms)
1) 2 sec
2) 4 sec
3) 6 sec
4) 10 sec
A body is allowed to fall from a tower 320 m high. When the ball reaches half the way
acceleration due to gravity suddenly disappears. The velocity of the body after two seconds
= 10 m2
1) 80 ms
2) 100 ms
3) 60 ms
4) 56​

Answer 1

1)

Given :

Body is released from height of 100m & after 2 seconds acceleration due to gravity vanishes

To Find : Total time of flight

Solution :

It is given that object is released from height 100m & it falls under influence of gravity for next 2 seconds

So , In two seconds Distance travelled by body is

S = ut + 1/2 at²

S = 0 + 1/2 (10)(2)²

S = 20 m

=> Object has travelled 20m before gravity vanishes

Also , Velocity of body at t = 2 seconds

V = u + at

V = 0 + 10(2)

V = 20 m/s

Now, Distance left = 80 m

speed = 20 m/s

Time = 80/20 = 4 s

Hence , Total time of flight is 6 seconds .

2)

Given :

A body is allowed to fall from a tower 320 m high. When the ball reaches half the way

acceleration due to gravity suddenly disappears

To Find :

Velocity of body when 'g' dissapears

Solution :

Velocity of body after it travels half distance i.e. 160 m

V² - U² = 2aS

V² - 0 = 2(10)(160)

V² = 3200

V = 40√2 m/s

i.e. V = 56 m/s approx