1. Friction and Gravity

2. Warm up10/28  Define these words  Friction  Gravity  Mass  weight

3. Learning Objectives  Describe friction and identify factors that determine the friction between two objects.  Identify the factors that affect the gravitational force between two objects.

4. Would you like to be an astronaut and train to work in space? Working in Microgravity

5. Friction Friction is the force that two surfaces exert on each other when they rub against each other. What factors affect friction? Types of surfaces involved How hard the surfaces are pushed together 32 1

6. Types of Friction Sliding friction: surfaces sliding over each other Static friction: between objects that are not moving Fluid friction: solid object moving through fluid Rolling friction: object rolling over a surface

7. Types of Friction Static friction Rolling friction Fluid friction Sliding friction

8. Force of Gravity Gravity is a force that pulls objects toward each other. Law of universal gravitation: Force of gravity acts between all objects in the universe that have mass. Friction Gravity

9. Factors Affecting Gravity 1.Mass: the amount of matter in an object SI unit is kilogram (kg) Mass = force (N) + acceleration (m/s) 2.Distance: how far apart objects are

10. Factors Affecting Gravity Mass The more mass an object has, the greater the gravitational force between it and other objects Gravitational force also depends on the distance between the objects centers As distance increases, gravitational force decreases

11. Mass, Gravity, and Weight Mass is the amount of matter in an object. Weight is a measure of the force of gravity on an object. Weight varies with the strength of gravity. On the moon: On Mars: 10 N 20 N

12. Student Worksheet Answers