Question

The 5 kg red book is about to fall from a 2.1 m high bookshelf.

Answer 1

Answer:

$\boxed {\boxed {\sf 102.9 \ J}}$

Explanation:

Potential energy is the energy an object possesses due to position. The formula is:

$PE= m \times g \times h$

where m is the mass, g is the acceleration due to gravity, and h is the height.

We know the book is 5 kilograms and is on a 2.1 meter high bookshelf. Since this is on Earth, the acceleration due to gravity is 9.8 meters per square second.

• m= 5 kg
• g= 9.8 m/s²
• h= 2.1 m

Substitute the values into the formula.

$PE= 5 \ kg \times 9.8 \ m/s^2 \times 2.1 \ m$

Multiply the numbers together.

$PE= 49 kg *m/s^2 *2.1 \ m$

$PE= 102.9 \ kg*m^2/s^2$

• 1 kilogram square meter per square second ( 1 kg*m²/s²) is equal to 1 Joule (J).
• So, our answ er of 102.9 kg*m²/s² is equal to 102.9 J

$PE= 102.9 \ J$

The book has 102.9 Joules of gravitational potential energy.

Answer 2

Answer:

w = d×f = 2.1 × ( 5×9.8)= 102.9J

Explanation:

because the question is asking for the energy PE