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!

Gravitational ForceEquation

• 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,

• m1 is the mass of the first point mass,

• m2 is the mass of the second point mass, and

• r is the distance between the two point masses.

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.

Gravitational Force• Gravitational force is weaker than other

types of forces, even though it holds the planets, stars, and galaxies together.

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.

• Introduction to Gravity - YouTube.mp4

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.

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.

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.

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.

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.