# Thread: antiderivative world problem

1. ## antiderivative world problem

A stone is dropped from the top of a 450 m tower. (Acceleration due to gravity is -9.8 m/s2. Ignore air resistance. Give your answers correct to two decimal places.)

(a) Find the distance of the stone above ground level at time t.
$s(t)=$ $450 - \frac{9.81t^2}{2}$

(b) How long does it take the stone to reach the ground?

$0 = 450 - \frac{9.81t^2}{2}$

$t = \sqrt\frac{(2 * 450)}{ 9.81}$
= $9.58 sec.$

(c) With what speed does it strike the ground? This is the part I keep getting wrong.

$
v(t)=-9.8t$

= $-9.8(9.58)$
= $-93.97$

2. Originally Posted by hazecraze
A stone is dropped from the top of a 450 m tower. (Acceleration due to gravity is -9.8 m/s2. Ignore air resistance. Give your answers correct to two decimal places.)

(a) Find the distance of the stone above ground level at time t.
$s(t)=$ $450 - \frac{9.81t^2}{2}$

(b) How long does it take the stone to reach the ground?

$0 = 450 - \frac{9.81t^2}{2}$

$t = \sqrt\frac{(2 * 450)}{ 9.81}$
= $9.58 sec.$

(c) With what speed does it strike the ground? This is the part I keep getting wrong.

$
v(t)=-9.8t$

= $-9.8(9.58)$
= $-93.97$
speed is a scalar > 0