# Newton's Law of Universal Gravitation Universal Forces Four Universal Forces: Strong Nuclear Force Weak Nuclear Force Electromagnetic

Force Gravitational Force Strong Nuclear Force Force inside nucleus that holds protons together. Like charges repel and

this force overcomes that to hold it together Weak Nuclear Force Force that is responsible for radioactive decay Types of decay

-alpha: release of alpha particle (He nucleus) -beta: release of electron -gamma: release of light Mass Energy Equivalence

E=mc2 Mass and energy can be converted into each other. When mass decreases in a nuclear reaction (fission or fusion) energy is given off Electromagnetic Force

Waves that transfer energy Responsible for light, communications, electricity and magnetism

Newtons Law of Universal Gravitation Physics Weakest of all forces

Long range force All objects in the universe are attracted to all other objects in the universe. The are affected by two factors: 1. mass 2. distance

Newton and Gravity Besides the 3 laws of motion Newton came up with the Law of Gravitation between objects Every particle in the universe exerts an attractive force on every other particle. This law means that every object that has mass exerts a gravitational force on other objects that

enter its gravitational field If the cannonball were in orbit around the planet, what would it take to bring it back from orbit? Newtons Discovery

If objects are spread far apart the force of gravity will decrease. If the objects are brought closer together the force of gravity will increase Distance & Force are Inversely related If the mass of one of the objects

increases then the gravitational force will also increase. Mass & Force are Directly Related The Law of Universal Gravitation

m1m2 FG G 2 d G = 6.67 x 10-11 Nm2/kg2 (universal gravitation constant ) FG = Force of Gravity between two objects (Newtons)

m = mass of the objects (kg) d = distance between objects (m) Inverse Square Law What does this mean? If the distance is

doubled then the Gravitational force will decrease by 1/4th of what it was. If the distance is halved then the Gravitational force will be 4 times as

great. A.K.A. Inverse Square Law m1m2 FG G 2 d

How Force is affected Calculate the Force between you and the Earth using the following: mearth = 6 x 1024 kg rearth = 6.4 x 106 m

Calculate your mass in kilograms Solve for the Gravitational force between you and the earth. How does this value compare to your weight in Newtons? Is there a Gravitational force

between you and your neighbor? Take measurements and find out using the Law of Gravitation. Einstein and Gravity In the early 20th century, Einstein took Newtons

concepts of gravity and proposed his theory of General Relativity. Einstein accurately described the deflection of light from massive objects. An eclipse in 1919 demonstrated what Einstein predicted- light is bent by gravity.