Question

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?

Answer 1

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