1. Gravity, Weight, Mass, Falling Objects, and Centripetal Force

2. Law of Gravitation

3.  Any 2 masses exert an attractive force on each other.  Force of gravity increases with mass and decreases with distance.

4. Weight vs. Mass

5.  Weight is the gravitational force exerted on an object by the Earth.  Weight is a force, and mass is a measure of the amount of matter an object contains.  Your mass is the same no matter where in the universe you are, but your weight will vary because of gravity.

6. Calculating Weight  Weight is your mass multiplied by the acceleration due to gravity (g) or 9.8 m/s 2.  The formula for weight is: weight = mass x g Where g = 9.8 m/s 2

7. Weight and Mass Celestial Body Gravitation Factor Relative to Earth Sun27.9 Mercury0.38 Venus0.91 Earth1 Moon0.17 Mars0.38 Jupiter2.54 Saturn1.08 Uranus0.91 Neptune1.19 Pluto0.06

8. Falling Objects

9. Air Resistance The air resistance of an object depends on its size, shape, and speed. Air resistance and NOT the mass of an object is why certain things fall more quickly than others. In a vacuum, there is NO air resistance, so all things fall at the same rate.

10. In a Vacuum

11. Exit Ticket 1.Why do you feel the force of attraction between you and the Earth, but not between you and your pencil? 2.What is the difference between weight and mass? 3.What is a vacuum and how do objects fall differently in a vacuum?

12. Projectile Motion  The path that an object takes when it is thrown or shot through the air.  This path is due to Earth’s gravitational pull and the object’s own inertia.

13. Projectile Motion

14. Terminal Velocity  As an object falls, it accelerates and its speed increases as does the force of air resistance.  The force of air resistance increases until it cancels out the force of gravity.  When the forces are balanced, the object no longer accelerates, so it reaches a constant speed called its terminal velocity.

15. Centripetal Force and g’s

16. Centripetal Force  Centripetal force is an unbalanced force pushing or pulling an object towards the center of a circle.  Centripetal acceleration is acceleration towards the center of a curved or circular path.

17. Centripetal Force examples from physicsclassroom.com As a car makes a turn, the force of friction acting upon the turned wheels of the car provides centripetal force required for circular motion. As a bucket of water is tied to a string and spun in a circle, the tension force acting upon the bucket provides the centripetal force required for circular motion. As the moon orbits the Earth, the force of gravity acting upon the moon provides the centripetal force required for circular motion.

18. No centripetal force example from physicsclassroom.com Without a centripetal force, an object in motion continues along a straight-line path. With a centripetal force, an object in motion will be accelerated and change its direction.

19. Weightlessness