Question

.A stone, allowed to fall under gravity falls 5t^2 metres
in t seconds. Find the distance travelled by the stone
in the last two seconds before it reaches the ground,
if the stone is dropped from a height of 180 m.
(A) 30 m (B) 60 m (C) 100 m (D) 90 m​

Answer 1

Answer:

options:

a)30m b)60m c)100m d)90m

MyApproach:

I am not able to think logically how to use the formula to solve the problem.

Given,

1/2 g . t2=5t2

5t2= 180

=>t=6

To calculate the distance in the last 2 sec I did 5 . (6)2-5 . (4)2=100m

Answer 2

Answer:

100 m

Step-by-step explanation:

Distance travelled by the stone in the last two seconds

before it reaches the ground be x.

5t^2 = 180

t^2 = 36 -> t = +6

x = 5(6)^2 – 5(4)^2

= 5(6^2 – 4^2) = 5(20) [ distance travelled by stone in 6 sec - dist. travelled by stone in 4 sec]

x= 100 m