Question

to estimate the height of a bridge over a river.A stone is dropped freely in the river from the bridge .A stone takes 2 seconds to touch the water surface in the river. Calculate the height of the bridge from the water level.

Answer 1

Given that,

u (initial velocity) = 0 m/s

t = 2 seconds

a = 9.8 m/s²

From second law of motion,

S = ut + 1/2(at²)

Substituting the values of u, t and a

S = 0*2 + 1/2( 9.8 * 2 * 2)

S = 0 + 1/2(39.2)

S = 19.6 meters

so, the height of bridge is 19.6 meters

Answer 2

Answer:19.6 m

Explanation:Given that,

u (initial velocity) = 0 m/s

t = 2 seconds

a = 9.8 m/s²

From second law of motion,

S = ut + 1/2(at²)

Substituting the values of u, t and a

S = 0*2 + 1/2( 9.8 * 2 * 2)

S = 0 + 1/2(39.2)

S = 19.6 meters

so, the height of bridge is 19.6 meters