1. Gravity Gravity is the force that pulls objects toward the center of the earth.

2. Gravity But…it goes beyond just that…….

3. Gravity Newton’s greatest discovery! The Law of Universal Gravitation. –Every mass attracts every other mass with a force that is proportional to the product of the two interacting masses –Force ~ (mass 1 x mass 2 ) / distance 2 –Force decreases with the inverse square of distance

4. Gravity Free fall is when the only force acting on an object is gravity. All objects in free fall accelerate at the same rate regardless of mass Demos

5. Gravity Fluid friction in the air is called “Air Resistance” In air, an object in free fall will continue to accelerate until the force of air resistance equals the force applied due to gravity. The greatest velocity of a free fall object in air is called “Terminal Velocity”

6. Gravity Weight is the measure of the force of gravity on an object. Mass is a measure of the amount of matter in that object

7. Gravity Weight is expressed with the equation: Newtons(N) = mass x acceleration due to gravity. 1N = 1Kg x 1 m/sec 2 9.8N = 1Kg x 9.8m/sec 2

8. Gravity Example: –A 100Kg person weighs…….. –(N) = mass x acceleration due to gravity –100kg x 9.8m/s 2 –So…….a 100Kg person weighs 980N on the Earth’s surface

9. Gravity Potential Energy is the energy an object has because of it’s position in a force field, such as a gravitational field.

10. Gravity Gravitational Potential Energy (GPE)= Weight x Height GPE is expressed as Newton Meters Nm.

11. Gravity Since we know that weight = mass x acceleration due to gravity. Logically…….. GPE = mgh (mass x Acceleration due to gravity x height) Demo..penny shot

12. Gravity As an object falls, it’s GPE turns into…… Kinetic Energy, the Energy of motion Kinetic Energy(KE) = 1 / 2 mass x velocity 2 KE = 1 / 2 mv 2

13. Not really Gravity….Oh well! Momentum is the product of a objects mass and its velocity. Momentum = Mass x velocity

14. Not really Gravity….Oh well! Conservation of Momentum –The total momentum of any group of objects remains the same unless outside forces act on the objects.