Question

A stone is throw vertically up from a bridge with velocity 3ms.If it strikes the water under the bridge after 2s,the bridge is at the height of (g=10ms^2)?

Answer 1

u is given = 4.9 , total time of flight = 2sec

   applying ,  S = ut + at2/2 ,

S = H = ? , a=-g , u=+4.9m/s (upward)

putting these in above eq

  H = 4.9*2 - 9.8(4)/2 = 9.8m

Answer 2

U is given = 4.9 , total time = 2s

U= initial velocity

S= displacement

T= time

a= acceleration

applying , S = Ut +(1/2) at^2

S = H(height of the bridge) = ? , a= retadation , U=4.9m/s (upward)

By the condition,

H = 4.9*2 - 9.8(4)/2 = 9.8m

》 So the height of the bridge is 9.8m