Chapter 2 - Forces Lesson 1 – The Nature of Force

Vocabulary Force: a push or pull Newton (N): SI unit for force Named after Sir Isaac Newton Force is described by it’s strength and by the direction in which it acts Force is going to the left. Force is going to the right. The force moving to the right is stronger then the force moving to the left.

How do forces affect Motion? Unbalanced Forces Balanced Forces A nonzero net force causes a change in the object’s motion.

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Chapter 2 - Forces Lesson 2 – Friction and Gravity

Friction The force that two surfaces exert on each other when they rub against each other

What affects Friction? 1.Type of surface 2.How hard the surfaces are pushed together. In general, smooth surfaces create less friction than rough surfaces and friction increases when surfaces push harder against each other.

Types of Friction Includes Air

More examples: Rolling Friction Static Friction Fluid friction Sliding Friction

What affects Gravity? Gravity is the force that pulls objects toward each other. Acts everywhere in the universe, not just Earth Law of Universal Gravitation – States that the force of gravity acts between all objects in the universe that have mass. Two Factors that affect gravitational attraction between objects – mass and distance

Factors affecting Gravity continued… Mass (kg) – the amount of matter in an object. The more mass an object has, the greater gravitational force between it and other objects. As distance increases, gravitational forces decreases. Mass (kg) – the amount of matter in an object. The more mass an object has, the greater gravitational force between it and other objects. As distance increases, gravitational forces decreases. Gravitational forces is small between objects with small masses. Gravitational force is larger between Objects with larger masses.

Elephant vs. Cat Elephant – has more mass Cat – Has less mass The amount of gravity between the Elephant and Earth is greater than the amount of gravity between a cat and Earth – That’s why we can pick up a cat!

Weight vs. Mass Weight is the force of Gravity on an object.