Question

A body falls from a height of 100 m. After 2 seconds if gravity disappears, find the total time it would take
to reach the ground (take g = 10 ms-2).
(1) 2 s
(2) 4 s
(3) 6 S
(4) 8s​

Answer 1

Step-by-step explanation:

H = = 100 meters

v = u + g t 

   = 0 + 10 m/s/s * 2 sec = 20 m/s

distance traveled in 2 sec 

  s = u t + 1/2 g t^2 = 0 + 1/2 *  10 * 2^2 = 20 meters

Distance to travel = 100 - 20 = 80 m

velocity = 20 m/sec   is constant as there is no gravity.

time taken = 80 m/ 20 m/s   = 4 seconds

Answer 2

Answer:

6s

Step-by-step explanation:

Initial stage,

t=0s, h=100m, a=9.8m/s²,u=0m/s

At 2s,

t=2s,h=?,v=?

Distance travelled in 2s, d= ut+1/2at²

d=0+1/2x9.8x2²=9.8x2=19.6m

h=100-d=100-19.6=80.4m

v=u+at=0+9.8×2=19.6m/s

After 2s,

h=80.4m, u=19.6m/s, a=0m/s²,t=?

h=ut+1/2at²

80.4=19.6t+0

t=80.4/19.6=4.11s≈4s

total time = 4s+2s=6s