When t= 1 a stone B is thrown vertically upwards from ground level with speed 5ms (ii) find t when a and b collide

i don't know if this is good for you but

Explanation:

ignoring frictional air resistance (drag) the speed on return is the same as when it left the ground (5 m/s but in the opposite direction).

Note: this points out a good reason for not firing live bullets into the air..they will return somewhere and at the same speed.

However, if you take into account the atmospheric drag the reurn speed will be somewhat smaller (but in the case of a bullet, probably still lethal.) Drag depends on many factors and is difficult to calculate.

layers of the earth affect the waves and these effects are seen on instruiments such as seimometers

ok

explanation: