A ball is thrown from a height of 67 meters with an initial downward velocity of 5/ms. The ball's height h (in meters) after t seconds is given by the following h=67-5t-5t^2. How long after the ball is thrown does it hit the ground?

Question

Mathematics

Abraham Church

19 March, 03:24

A ball is thrown from a height of 67 meters with an initial downward velocity of 5/ms. The ball's height h (in meters) after t seconds is given by the following h=67-5t-5t^2. How long after the ball is thrown does it hit the ground?

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Tyshawn Mckee · Answer 1

3.19459 seconds

Since we've been given the equation for how high the ball is at t seconds, all we need to do is solve for a height of 0. So h = 67 - 5t - 5t^2 0 = 67 - 5t - 5t^2 And you should immediately notice that we have a quadratic equation with A = - 5, B = - 5, and C=67. Use the quadratic formula to determine the roots of - 4.19459 and 3.19459. Since we can't have negative seconds, that means that the ball will hit the ground 3.19459 seconds after it was thrown.