+0  
 
+1
53
1
avatar+117 

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.

xXxTenTacion  Jul 8, 2018
 #1
avatar
0

Solve for t:
56 = 60 t - 16 t^2

56 = 60 t - 16 t^2 is equivalent to 60 t - 16 t^2 = 56:
60 t - 16 t^2 = 56

Divide both sides by -16:
t^2 - (15 t)/4 = -7/2

Add 225/64 to both sides:
t^2 - (15 t)/4 + 225/64 = 1/64

Write the left hand side as a square:
(t - 15/8)^2 = 1/64

Take the square root of both sides:
t - 15/8 = 1/8 or t - 15/8 = -1/8

Add 15/8 to both sides:
t = 2 or t - 15/8 = -1/8

Add 15/8 to both sides:
t = 7/4 = 1.75 seconds. But after 1.75 seconds it continues to go up for about 1/4 foot. And coming down to 56 feet again at exactly t= 2 seconds.

Note: somebody should check this.

Guest Jul 8, 2018

17 Online Users

avatar
avatar

New Privacy Policy

We use cookies to personalise content and advertisements and to analyse access to our website. Furthermore, our partners for online advertising receive information about your use of our website.
For more information: our cookie policy and privacy policy.