Question

Need some help with this Calculus 1 question

Answer 1

The stone reaches a height of 13 m when
`h=13`:

`8t-0.83t^2=13\implies t\approx2.069\text{ or }t=7.569`

The question refers to the moment at which it **rises** to 13 m, so we need to take the earlier instance,
`t\approx2.069` seconds after the stone is tossed.

The stone's velocity is given by the derivative of its height function:

`v(t)=h'(t)=8-1.66t`

Plug in the time found above; the stone's velocity at this moment is about 4.57 m/s.