1. Fundamental Forces We have talked about a lot of different kinds of forces. Gravitational, friction, normal, fluid resistance, tension… Are these all actually different in nature? Four fundamental forces (we think): Gravitational Electromagnetic Strong Weak All interactions arise through one of these fundamental forces. All of the interactions we have dealt with so far were electromagnetic or gravitational.

2. Chapter 5 Summary Applying Newton’s Laws

3. Chapter 6 Outline Work and Kinetic Energy Work and energy Conservation of energy Kinetic Energy Work-energy theorem Work with varying forces Power Fundamental forces

4. Work and Kinetic Energy In everyday conversation, work would be any activity that requires some effort. In physics, work is something that is done to change the energy of an object. Energy can take many forms. Consider the case of applying a force on a body. As we saw last chapter, the body will accelerate. Its kinetic energy, or energy of motion, will increase. If we apply the force over a longer distance, we increase the kinetic energy more.

5. Work and Forces

6. Work and Forces Not Aligned with Displacement

7. Sign of Work Work is a scalar. It does not indicate a direction, but its sign is still quite important. The sign of the work done on an object depends on the direction of both the force and the displacement. If the force and the displacement are in the same direction, the work done by the force on the body is positive. It is crucially important to indicate who/what is doing the work and who/what the work is done upon.

8. Total Work In general, there are often more than one force acting on an object. The total work done on the object depends on the net force and the displacement of the object. Multiple forces/bodies can do different, sometimes opposing, amounts of work on the body.

9. Work Example

10. Kinetic Energy When a force is applied to a body, it causes an acceleration. A force applied over a distance, as we have said is the definition of work. This changes the kinetic energy of the object. How can we relate work done to change in kinetic energy?

11. Kinetic Energy When a force is applied to a body, it causes an acceleration. A force applied over a distance, as we have said is the definition of work. This changes the kinetic energy of the object. How can we relate work done to change in kinetic energy?

12. Work-Energy Theorem

13. Work-Energy Example