When you lift a book from the ground to your desk, what kind of work do you do, negative or positive? By lifting the book, what do you change? Does the book gain or lose energy? What kind of energy?

Second question: A ball with a mass of 5.0g is moving at a speed of 2.0 m/s. Would doubling the mass or doubling the speed have a greater effect on the kinetic energy of the ball? Explain.

When you lift a book from the ground to your desk, you do positive work. By lifting the book, you are increasing the object's gravitational potential energy. The book gains energy. It is gravitational potential energy.

Explanation:

Positive work is said when the force exerted on the object is in the same direction as that of the direction of its displacement.

Negative work is said to be done when the force exerted on the object is in the opposite direction as that of the direction of its displacement.

In this case, the force exerted on the book is in the upward direction and is in the same direction as that of its displacement. Hence, we are doing a positive work. Gravity is doing a negative work.

When we lift the book, we are changing its location from ground to the desk and in this process, the book is gaining energy. The energy gained by the object is gravitational potential energy.

Gravitational potential energy is the energy which is possessed by the virtue of the object's position of location.