Forces

1. Forces

2. First we need to define the word FORCE: • The cause of motion (what causes objects to move) • Two types of forces • - Pushes • - Pulls

3. Forces are measured in Newtons • SI unit of force • Symbol: N • Measured by using a spring scale

4. Forces may be balanced or unbalanced • Balanced forces – all forces acting on an object are equal • -There is NO MOTION • Unbalanced forces – one or more forces acting on an object are stronger than others • -There is MOTION • A NET FORCE

5. Friction Force that slows down motion. There are three different types of friction: 1. Rolling Friction 2. Sliding Friction 3. Fluid Friction

6. Rolling Friction The friction that exists when a wheel turns on a surface.

7. Sliding Friction When two objects are rubbing against each other.

8. Fluid Friction The friction on a solid object as it moves through water.

9. Gravity • Force that attracts all objects toward each other • More mass = more gravity • Acceleration because of gravity is 9.8 m/s/s • All objects accelerate at the same rate

10. Newton’s Laws • First Law – Inertia • Second Law – Acceleration, Force & Mass • Third Law – Action-Reaction

11. First Law • Inertia • An object at rest [not moving] remains at rest unless acted on by a force [push or pull] • An object in motion remains in motion unless acted on by a force [push or pull]

12. First Law • Inertia & Mass • Mass is the amount of matter in an object • The more MASS an object has, the more INERTIA the object has. • Bigger objects are harder to start & stop

13. Second Law • Acceleration & Force • The more force placed on an object, the more it will accelerate [change its motion] • Acceleration & Mass • The more mass [or inertia] an object has, the more force it takes to accelerate the object

14. Third Law • Action – Reaction • Forces are always produced in pairs with opposite directions & equal strengths • For every force there is an equal and opposite force