1. Forces NL 3.1

2. Force is a push or pull in a particular direction – Forces have different magnitudes and directions Motion is an object’s change in position over time. Forces cause a change in motion REFRESHER

3. What are examples of forces that we see on earth every day?

4. Friction is the force that holds back the movement of a sliding object. It acts in the opposite direction of the way an object wants to slide.

6. http://vimeo.com/50104053

7. Gravity or gravitational forces are forces of attraction. Earth pulls on you to keep you on the ground Every object that has mass exerts a gravitational pull on every other mass – The size of the pull depends on the masses of the objects – This is what holds moons to their planets and the planets to our Sun.

8. Gravity is what causes an object to fall to the ground. In a vacuum (where there is no air) a feather will fall at the same speed as a dense ball

9. Momentum is an indication of how hard it would be to stop an object. – When the mass is greater (at the same speeds) the momentum is greater. – Think about the ping pong ball and golf ball. They had the same volume, and relatively the same speed. Which one was harder to stop?

10. Just like in Newton’s 1 st Law, momentum will remain the same unless acted upon by an outside force – When that happens we say that momentum is conserved – This is why the golf ball moved the block. The greater mass had a greater momentum which could only be stopped when it hit that wooden block.