High School

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 per second squared, how far above the ground [tex]h[/tex] was the hammer when you dropped it? Use the formula:

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

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

Answer :

To solve this problem, we use the formula for the final velocity of a falling object:

[tex]\[ v = \sqrt{2 \cdot g \cdot h} \][/tex]

Where:
- [tex]\( v \)[/tex] is the final velocity when the object hits the ground.
- [tex]\( g \)[/tex] is the acceleration due to gravity, which is 32 feet per second squared (given).
- [tex]\( h \)[/tex] is the height from which the object was initially dropped.

We are given that the velocity [tex]\( v \)[/tex] is 12 feet per second when the hammer hits the ground.

Our goal is to find [tex]\( h \)[/tex].

1. First, square both sides of the formula to eliminate the square root:

[tex]\[ v^2 = 2 \cdot g \cdot h \][/tex]

2. Next, isolate [tex]\( h \)[/tex] by dividing both sides by [tex]\( 2 \cdot g \)[/tex]:

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

3. Substitute the known values into the formula:

- [tex]\( v = 12 \)[/tex] feet per second
- [tex]\( g = 32 \)[/tex] feet per second squared

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

4. Calculate [tex]\( 12^2 \)[/tex], which is 144.

5. Multiply [tex]\( 2 \cdot 32 \)[/tex] to get 64.

6. Finally, divide 144 by 64 to find [tex]\( h \)[/tex]:

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

Thus, the hammer was dropped from a height of 2.25 feet. Therefore, the correct answer is:

C. 2.25 feet