College

You are helping with some repairs at home. You drop a hammer, and it hits the floor at a speed of 12 feet per second. If the acceleration due to gravity [tex]g[/tex] is 32 feet/second[tex]\(^2\)[/tex], how far above the ground [tex]h[/tex] was the hammer when you dropped it? Use the formula: [tex]v=\sqrt{2gh}[/tex]

A. 8.5 feet
B. 1.0 foot
C. 18.0 feet
D. 2.25 feet

Answer :

We start with the formula for the final velocity when falling from rest:

[tex]$$
v = \sqrt{2gh}
$$[/tex]

where
[tex]\( v = 12 \)[/tex] feet per second (speed when the hammer hits the floor)
[tex]\( g = 32 \)[/tex] feet per second squared (acceleration due to gravity)
[tex]\( h \)[/tex] is the height above the ground.

Step 1: Square both sides of the equation.

[tex]$$
v^2 = 2gh
$$[/tex]

Step 2: Solve for [tex]\( h \)[/tex].

[tex]$$
h = \frac{v^2}{2g}
$$[/tex]

Step 3: Substitute the given values.

[tex]$$
h = \frac{12^2}{2 \times 32}
$$[/tex]

Step 4: Compute [tex]\( 12^2 \)[/tex] and the denominator.

[tex]$$
12^2 = 144, \quad 2 \times 32 = 64
$$[/tex]

Step 5: Divide to find [tex]\( h \)[/tex].

[tex]$$
h = \frac{144}{64} = 2.25 \text{ feet}
$$[/tex]

Thus, the hammer was dropped from a height of [tex]$2.25$[/tex] feet above the ground.

The correct answer is therefore option D: [tex]$2.25$[/tex] feet.