SOLUTION: A projectile is fired directly upward with a muzzle velocity of 860 feet per second from a height of 7 feet above the ground. a. Determine a function for the height of the proje

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Question 217218: A projectile is fired directly upward with a muzzle velocity of 860 feet per second from a height of 7 feet above the ground.
a. Determine a function for the height of the projectile t seconds after it's released.
b. How long does it take the projectile to reach of height of 100 feet on its way up?
c. How long is the projectile in the air?
Answer by ankor@dixie-net.com(22740) (Show Source):
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A projectile is fired directly upward with a muzzle velocity of 860 feet per
second from a height of 7 feet above the ground.
:
a. Determine a function for the height of the projectile t seconds after it's released.
Assuming the equation: h = -16t^2 + vt + c
h = -16t^2 + 860t + 7
;
b. How long does it take the projectile to reach of height of 100 feet on its way up?
-16^2 + 860t + 7 = 100
-16t^2 + 860t + 7 - 100 = 0
-16t^2 + 860t - 93 = 0
Use the quadratic formulas to find t

In this equation: x = t: a=-16; b=860; c=-93

Do the math here and you get: t =.108 seconds for 100' on the way up
:
c. How long is the projectile in the air?
h = 0, the equation for this -16t^2 + 860t + 7 = 0
Use the quadratic formulas to find t

In this equation: x = t: a=-16; b=860; c=7

Do the math here and you get: t = 53.758 seconds to return to earth