GRAVITY

1. GRAVITY What goes up, must come down??

2. Tuesday Gravity Is it possible for some basketball players to “hang” in the air during a dunk? Give your opinion http://www.youtube.com/watch?v=vZqVq5LrdQQ

3. WHAT IS GRAVITY? • Gravity is a FORCE • Gravitational attraction pulls all objects towards each other. • The force can be STRONG or WEAK . • The strength of gravitational force depends on : MASS & DISTANCE

4. THE RELATIONSHIP BETWEEN MASS, DISTANCE AND GRAVITATIONAL FORCE • IF YOU INCREASE THE DISTANCE BETWEEN TWO OBJECTS DOES GRAVITATIONAL FORCE INCREASE OR DECREASE? • WHAT IF YOU INCREASE THE MASS OF THE OBJECTS? Hint: think of the Sun and the Moon

5. Relationships • As DISTANCE INCREASES, the gravitational force goes DOWN. • As MASS INCREASES, the gravitational force goesUP. • WHY does your gravitational force not pull objects toward you?

6. GRAVITY – fast facts • ALL OBJECTS with mass exert gravitational force. • Gravity causes falling objects to speed up (accelerate) as they fall : 9.8 m/s FASTER EVERY SECOND. Acceleration = 9.8 m/s2 • Gravity (and inertia) causes the Earth to orbit the sun and the Moon to orbit the Earth. • The gravitational pull of the sun and the moon creates tides on Earth (2 high & 2 low tides per day)

7. WEIGHT Another name for gravitational force of objects near Earth’s surface is WEIGHT • Remember Newton’s 2ND LAW: F = M X A • Because of gravity, objects fall at a constant ACCELERATION (9.8 m/s2) • So objects near the Earth surface have GRAVITATIONAL FORCE =MASSx9.8m/s2=WEIGHT

8. WEIGHT VERSUS MASS • WEIGHT AND MASS ARE DIFFERENT! • WEIGHT is a FORCE measured in Newtons. • When you step on a scale, you are measuring gravitational force. • Your weight changes depending on your location (Earth, the moon, etc). • MASS: is the AMOUNT OF MATTER IN AN OBJECT and does NOT depend on location