Question

The height of an arrow, shot directly upwards, is given by h = - 4.9t^2 + 20.5 t + 2 , where h is the height in metres and t is the time in seconds. When does the arrow hit the ground, to the nearest tenth of a second? Solve using quadratic relations

Answer 1

At the point where the arrow hits the ground , it has no height above the ground.

We say , h=0

`-4.9t^2+20.5t+2=0`

We will solve the quadratic and obtain a value for t

The solution to the quadratic are t= - 0.095 and t=4.28

Since time function cannot be negative , we agree that

`t=4.3\text{ }seconds`