SOLUTION: Catapults fire projectiles that form a parabolic path. The height(h) in metres above the ground t seconds after the projectile leaves the catapult is given by the formula h=-4.9t^2

Algebra ->  Quadratic Equations and Parabolas -> SOLUTION: Catapults fire projectiles that form a parabolic path. The height(h) in metres above the ground t seconds after the projectile leaves the catapult is given by the formula h=-4.9t^2      Log On


   

Question 121033: Catapults fire projectiles that form a parabolic path. The height(h) in metres above the ground t seconds after the projectile leaves the catapult is given by the formula h=-4.9t^2 +4.2t+8.Use the quadratic formula to find the length of time the projectile is in the air before it hits the ground.
Answer by ankor@dixie-net.com(22740) About Me  (Show Source):
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Catapults fire projectiles that form a parabolic path. The height(h) in metres above the ground t seconds after the projectile leaves the catapult is given by the formula h=-4.9t^2 +4.2t+8.Use the quadratic formula to find the length of time the projectile is in the air before it hits the ground.
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That looks like a very slow projectile, anyway
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h = 0 when it strikes the ground so we have:
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-4.9t^2 + 4.2t + 8 = 0
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Use the quadratic formula: a=-4.9; b=4.2 c=8
t+=+%28-4.2+%2B-+sqrt%284.2%5E2+-+4+%2A+-4.9+%2A+8+%29%29%2F%282%2A-4.9%29+
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t+=+%28-4.2+%2B-+sqrt%2817.4+-+%28-156.8%29+%29%29%2F%28-9.8%29+
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t+=+%28-4.2+%2B-+sqrt%2817.4+%2B+156.8+%29%29%2F%28-9.8%29+
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t+=+%28-4.2+%2B-+sqrt%28174.2+%29%29%2F%28-9.8%29+
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t+=+%28-4.2+-+13.1985%29%2F%28-9.8%29+
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t+=+%28-173985%29%2F%28-9.8%29
t = 1.775 second