Question

A stone lying at the edge of the road falls down into the river flowing below the road. If the stone takes 2 seconds to reach the river, then
(I) find speed with which the stone strikes the water surface in the river
(ii) the average speed at the end of the fall
(iii) the height of road from the river​

Answer 1

Answer:

Explanation:

Let's say that the vertical distance of river from road is h. Time taken for the stone to reach river is 2 seconds.

Using the below equation and putting u=0 (Because stone was at rest initially)

We get,

Where g is the acceleration due to gravity.

And using

h = 1/2gt²

we get h=20m

And putting value of h in above equation we get v=20m/s

Given-

t= 2s

g=9.8m/s

u=0m/s Because the stone is at rest

To find = height (distance covered by the rock)

Answer-

using the third formula of uniformly accelerated motion =

S = vt + 1/2× at^2

=s=(0×2) + (1/2 × 9.8 × 2 ×2)

=s= 0 + (2 × 9.8)

= s = 0 + 19.6

= s = 19.6 m

Since h is total distance covered HENCE s= h

Therefore h= 19.6 m