Chapter 4.2, Problem 18PP

To determine

To calculate: the gravitational potential energy of the textbook-Earth system relative to the floor.

Answer to Problem 18PP

The gravitational potential energy of the textbook-Earth system relative to the floor is $\underset{\_}{\text{98 J}}$ .

Explanation of Solution

Given data:

Mass of the textbook(placed on the desk), $m=8.0\text{ kg}$

Height of the desktop from the ground, $h=1.25\text{ m}$

Gravity, $g\text{ = 9}\text{.8}\text{}\text{}\text{ N/kg}$

Formula used:

Gravitational Potential Energy Equation:

  $GPE=mgh$

Where $GPE$ is the gravitational potential energy of the object in joules, $m$ is the mass of the object in $\text{kg}$ and $h$ is the height of the object in meters from the ground.

Calculation:

As per the problem,

  $\begin{array}{l}m=8.0\text{ kg}\\ g\text{= 9}\text{.8}\text{}\text{}\text{ N/kg}\\ h=1.25\text{ m}\end{array}$

Substitute the values of mass, gravity and height in the gravitational potential energy equation:

  $\begin{array}{l}GPE=mgh\\ GPE=(8.0\text{ kg)(9}\text{.8}\text{}\text{ N/kg)(1}\text{.25 m)}\\ GPE=98\text{ J}\end{array}$

Conclusion:

The gravitational potential energy of the textbook-Earth system relative to the floor is $\underset{\_}{\text{98 J}}$ .