Question

A stone dropped from the top of a cliff reaches ground level in 4s and buries
itself 0.8m into the mud. Calculate
1) Height of cliff
2) Final velocity of stone on reaching level and
3) Retardation produced by the mud. Take g=9.8m/s?​

Answer 1

Answer:

on analysing,

we get that that we have to find height of cliff,

v=u-gt

=> 0 =u -9.8*4

=> -u = -39.2 m/s

=> u= 39.2 m/s here,

we get u = 39.2 m/s

Total distance

S = height of cliff (h) + 0.8m.

Now,

S={v^2-u^2)/2g =

u^2/2*9.8 = (39.2)^2 /19.6

= 1536.64/19.6 = 78.4 m

then,

h= (78.4-0.8)m = 77.6 m