Question

A stone is dropped in a river from a bridge. If it takes 4 seconds to reach surface of water ,calculate the depth of the water level from the bridge .Also calculate the velocity with which the stone strikes on the water surface

Answer 1

The stone takes 4sec to reach the water level.

initial velocity (u)=0

time(t)=4s

acceleration due to gravity(a)=

9.8(10 approx)

so,its final velocity will be

v=u+at

0+10×4=40

v=40m/s

hey dude,

hope it helps you.

Answer 2

Answer:

78.6 m

39.2 m/s

Given:

time taken = 4 seconds

initial velocity = o m/sec

To find:

depth of the water level from bridge.

velocity with which the stone strikes on the water surface.

Step-by-step explanation:

First calculate final velocity.

according to equation of motion,

v = u + at

in this case a = g (9.8 m/s²)

t = 4 sec,

u = 0

⇒ v = u + at

⇒ v = 0 + 9.8 (4)

⇒ v = 39.2 m/sec

hence, velocity with which the stone strikes on the water surface is 39.2m/sec.

First calculate final velocity.

according to equation of motion,

s = ut + 1/2at²

s = 1/2 × 9.8 (4)²

s = 1/2 × 9.8 × 16

s = 8 × 9.8

s = 78.4 meters

hence, the depth of the water level from the bridge is 78.4.

Therefore, velocity with which the stone strikes on the water surface is 39.2m/sec and depth of the water level from the bridge is 78.4.

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