Tom drops a coin from the top of a building. tom is 90 meters from the ground when he drops the coin. a) what is the height of the coin exactly 3 seconds after he releases the coin?   b) when the coin hits the ground, how much time has passed from when it was dropped until impact with the ground?

Disregarding air friction, the distance traveled by an object due to gravity is : H = 0.5*g*t^2.   g is the gravitational constant at the surface of earth.  

g= 9.81 m/s^2  

After 3 seconds, Distance = .5*9.81*9 = 44.15 meters traveled.   

Since it was dropped from a height of 90 meters, the current height is 90 - 44.15 = (a) 45.85 meters  

(b) It has to travel 90 meters to hit the ground . So we must find t  

Using the same equation  

t = (2*H/g)^.5 

 t = (2*90/g)^.5 = 4.28 seconds until it hits the ground