+0  
 
0
80
2
avatar

The equation y = -16t^2 + 60t describes the height (in feet) of a projectile launched from the ground at 60 feet per second upward. In how many seconds will the projectile first reach 56 feet in height? Express your answer as a decimal rounded to the nearest hundredth.

 Nov 28, 2022
 #1
avatar
-1

Solving the quadratic, I get 2.86 seconds.

 Nov 28, 2022
 #2
avatar+33337 
+1

Set y = 56, so  56 = -16*t^2 + 60*t

 

Divide by 16 and rearrange this:   t^2 - (15/4)*t + (7/2) = 0

 

This factorises as (t - 7/4)*(t - 2) = 0

 

So, there are two times.  Which do you think represents the answer to the question?

 Nov 28, 2022

16 Online Users