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ahrayia [7]
3 years ago
9

Sean tossed a coin off a bridge into the stream below. The path of the coin can be represented by the equation 2 h tt = − 16t^2+

72t+ 100 (where t is time in seconds and h is height in feet) How long will it take the coin to reach the stream?
Mathematics
1 answer:
tekilochka [14]3 years ago
3 0

Answer:

It will take 5.61 seconds for the coin to reach the stream.

Step-by-step explanation:

The height of the coin, after t seconds, is given by the following equation:

h(t) = -16t^{2} + 72t + 100

How long will it take the coin to reach the stream?

The stream is the ground level.

So the coin reaches the stream when h(t) = 0.

h(t) = -16t^{2} + 72t + 100

-16t^{2} + 72t + 100 = 0

Multiplying by (-1)

16t^{2} - 72t - 100 = 0

Solving a quadratic equation:

Given a second order polynomial expressed by the following equation:

ax^{2} + bx + c, a\neq0.

This polynomial has roots x_{1}, x_{2} such that ax^{2} + bx + c = a(x - x_{1})*(x - x_{2}), given by the following formulas:

x_{1} = \frac{-b + \sqrt{\bigtriangleup}}{2*a}

x_{2} = \frac{-b - \sqrt{\bigtriangleup}}{2*a}

\bigtriangleup = b^{2} - 4ac

In this question:

16t^{2} - 72t - 100 = 0

So

a = 16, b = -72, c = -100

\bigtriangleup = (-72)^{2} - 4*16*(-100) = 11584

t_{1} = \frac{-(-72) + \sqrt{11584}}{2*16} = 5.61

t_{2} = \frac{-(-72) - \sqrt{11584}}{2*16} = -1.11

Time is a positive measure, so we take the positive value.

It will take 5.61 seconds for the coin to reach the stream.

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