A stone is shot straight upward with a speed of 20 m/sec
from a tower 200 m high. The speed with which it strikes
the ground is approximately
(a) 60 m/sec
(b) 65 m/sec
(c) 70 m/sec
(d) 75 m/sec
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A stone is shot straight upward with a speed of 20 m/sec
from a tower 200 m high. The speed with which it strikes
the ground is approximately
(a) 60 m/sec
(b) 65 m/sec
(c) 70 m/sec
(d) 75 m/sec
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Final speed v= 0
Initial speed u = 20m/s
acceleration g= -g=-10 (approx.)
Apply third law of motion,
v^2-u^2=2as
so distance/height covered..
s=(v^2-u^2)/2a
so s=(0-400)/2x(-10)=-400/-20=20m
(the top height from the tower)
now to hit the ground=u =0, s=220m
again by 3rd law,
v^2=0^2+2×10×220
v^2=4400
v=66m/s (approx.)
i hope it will help