Show how to set up and solve for each part.

Question

David drops a ball from a bridge at an initial height of 100 meters. (a) What is the height of the ball to the nearest tenth of a meter exactly 3 seconds after he releases the ball?
(b) How many seconds after the ball is released will it hit the ground?

Answer 1

(a)

 

h(t) = h₀ - gt²/2

 

h₀ = 100 m

9 = 9.8 m/s²

t = 3 sec

 

Just plug in the numbers and get h(3).

 

(b)

 

Set

 

h₀ = gt²/2

 

and solve for t.  Plug in the numbers for h₀ and g, and get t in seconds.