Question

A ball is projected vertically upwards with a velocity of 40 m/s from the top of a cliff 100 m high .Find the total time taken the ground.

• A. 4 sec
• B. 8 sec
• C. 15.8 sec
• D. 12 sec

Answer 1

The correct option is C 15.8 sec

Here height of cliff is =100m

The distance travelled by stone =100+X-X

V=40m/s

S=ut +1÷2At²

100=0×t+1÷2at².........(1)

V²= u²+2as

40 =2a100

2a=40÷100

a=0.4÷2

=0.2

100=2×0.2×t²

100=0.4×t²

t²=100÷0.4

t=15.8