Question

Long word problem, bare with me

Julian kicked a soccer ball into the air with an initial upward velocity of 40 feet per second. The height (h) in feet of the ball above the ground can be modeled by h= -16t^2+40t, where (t) is the time in seconds after Julian kicked the ball. Find the time in takes the ball to return to the ground. HINT: FACTOR AND THEN SOLVE FOR (t).


A: 2/5s

B: 1 and 1/3s

C 1 and 3/4s

D 2 and 1/2s

Answer 1

5/2 seconds

Explanation:

The ball will return to the ground when the height is 0. So we set the height function to 0 and solve for t.

`-16t^2+40t=0\\16t^2-40t=0\\8t(2t-5)=0\\So\\2t-5=0\\2t=5\\t=(5)/(2)`

t is 5/2 seconds. This is when the ball returns to the ground.

Note: I believe it should be answer choice A and there is a mistake in the answer