Question

A stone is dropped from the top of a 40m height of tower calculate the speed after 2 sec? Also find the speed with which the stone strike the ground?

Answer 1

v=u-gt
v= -10×2= -20=20m/s {aprox.)

speed when it strike the ground
v=√2gh
v=√2×10×40
v=√800
v=20√2m/s (aprox)

Answer 2

speed after 2 sec v = u+at =0 +9.8×2 =19.6m/s
speed with which it will strike the ground
v²-u²=2as
v² = 0 + 2×9.8×40 =784
v = 28 m/s