a person standing on the roof of a 40 m high tower, throws a ball vertically upwards with speed 10m/s - Physics - Kinematics

Question

a person standing on the roof of a 40 m high tower, throws
a ball vertically upwards with speed 10m/s 2 seconds later, he
throws another ball again in vertical downward direction(g=10m/s^2)
if both hit the ground simultaneously, then choose the correct
options
a) the first ball hits the ground after 4 seconds
b) the second ball was projected vertically downwards with speed
5m/s
c) the distance travelled by the first ball is 10 m greater than
the distance travelled by the second ball
d) both balls hit the ground with same velocities

Shobhit Mittal · Accepted Answer

Dear Student,

for ball 2u, g=10 m/s2, S=4040=ut+10*t22u=10,a=-10m/s2, S=-40-40=10t+2-10*t+222t+2=T-40=10T-10*T22T2-2T-8=0T2-4T+2T-8=0TT-4+2T-4=0T= 4 secoption a is correct 
t=4-2=2 sec 40=2u+10*42u=10 m/s option b is wrong option C is correct
since both have the same initial speed the velocity will be same when they hit option d is correct 
regards