Question

A hang glider 25 meters above the ground starts to descend at a constant rate of 2 meters per second. Which equation shows the height h after t seconds of descent?

1. $h=25t+2t$
2. $h=-25t+2$
3. $h=2t+25$
   
4. $h=-2t+25$

Short answer

The required equation for height is $h=-2t+25$. The correct option is D.

Step-by-step solution

Step 1. State the concept.

The constant rate of descent gives a linear equation for the height.

Step 2. List the given data.

A hang glider 25 meters above the ground starts to descend at a constant rate of 2 meters per second.

Step 3. Write the equation.

The hang glider is initially at a height of 25 meters. So, at $t=0$, $h=25$.

The glider descends at a constant rate of 2 meters per second. Then, the height must be given as,

$h=-2t+25$

The negative sign is because the hang glider is descending, so the height is decreasing.

So, the required equation for height is $h=-2t+25$.