Chapter F1 :D

1. What is a force? Force is a push or pull.

2. Gravitational force: Any object on the Earth or at least close to Earth, will experience a gravitational force.

3. • Is not a force of contact.

4. What are the effects of forces? It changes the motion of a body or produce motion or stress in a stationary body.

5. • Acts toward the center of mass of an object (for Earth, this is toward the center of the Earth)

6. • Has magnitude given by mg (m is mass, g is gravitational acceleration).

7. There are several types of friction: • Dry friction • Fluid friction • Lubricated friction • Skin friction • Internal friction

8. Friction is the force resisting the relative motion of solid surfaces, fluid layers, and material elements sliding against each other.

9. Ways to reduce friction: Devices such as wheels, ball bearings, roller bearings, and air cushion or other types of fluid bearings can change sliding friction into a much smaller type of rolling friction.

10. Pressure is physical force exerted on or against an object by something in contact with it.

11. You can increase pressure by increasing the force exerted on the area of contact without changing the area of contact, or do not change the amount of force exerted on the area of contact but decrease the area of contact.

12. You can decrease pressure by decreasing the force exerted on the area of contact without changing the area of contact, or do not change the amount of force exerted on the area of contact but increase the area of contact.