1. Gravitational Force Gravitational force is the force of attraction between ALL masses in the universe; especially the attraction of the earth's mass for bodies near its surface. = Gravity –Gravity runs over any range and affects anything with mass. –The force of gravity is different from other forces, such as friction; the force of gravity acts even if objects do not touch!

2. Gravitational Force Equation The force is directly proportional to the product of the two masses and inversely proportional to the square of the distance between the point masses: where: F is the magnitude of the gravitational force between the two point masses, G is the gravitational constant, m 1 is the mass of the first point mass, m 2 is the mass of the second point mass, and r is the distance between the two point masses.

3. Gravitational Force Gravitational Force rapidly grows weaker as the distance between two objects increases. If the original distance is tripled, the gravitational force decreases to one-ninth its original value.

4. Gravitational Force Gravitational force is weaker than other types of forces, even though it holds the planets, stars, and galaxies together.

5. Gravitational Force Remember…. –The greater the mass, the stronger the force –The greater the distance between two objects, the weaker the gravitational force between them.

6. Introduction to Gravity - YouTube.mp4

8. Centripetal Force For an object moving in a circle, there must be an inward force acting upon it in order to cause its inward acceleration.

9. Centripetal Force The word centripetal means “center seeking” Object's moving in circular motion have a net force acting towards the center The centripetal force for uniform circular motion alters the direction of the object without altering its speed.

10. Centripetal Force 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.

11. Centripetal Force 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.

12. Centripetal Force: Orbit As the moon orbits the Earth, the force of gravity acting upon the moon provides the centripetal force required for circular motion.