Question

A book on a 2-meter high shelf has a mass of 0.4 kg. What is its potential energy?

Answer 1

Answer:

$\boxed {\boxed {\sf 7.84 \ Joules}}$

Explanation:

The formula for potential energy is:

$PE=m*g*h$

where m is the mass, g is the gravitational acceleration, and h is the height.

The mass of the book is 0.4 kilograms. The gravitational acceleration on Earth is 9.8 m/s². The height of the book is 2 meters.

$m=0.4 \ kg \\g=9.8 \ m/s^2 \\h=2\ m$

Substitute the values into the formula.

$PE=(0.4 \ kg)(9.8 \ m/s^2)(2 \ m)$

Multiply the first two numbers.

• 0.4 kg*9.8 m/s²= 3.92 kg*m/s²
• If we convert the units now, the problem will be much easier later on.
• 1 kg*m/s² is equal to 1 Newton. So, our answer of 3.92 kg*m/s² is equal to 3.92 N

$PE=(3.92 \ N )(2 \ m)$

Multiply.

• 3.92 N* 2 m=7.84 N*m
• 1 Newton meter is equal to 1 Joule (this is why we converted the units).
• Our answer is equal to 7.84 Joules.

$PE=7.84 \ J$

Answer 2

Answer:

7.84 is your answer ok bye