Four Universal Forces What is a force It

Four Universal Forces

What is a force? ¡ It can be a pull (attraction) or a push (repulsion)

Forces are Measured in……. . ¡Newton’s ¡ 1 N = 1 kg ▪ (N) 2 m/s

1 Electromagnetic Forces • Electric and magnetic forces are two different aspects of the electromagnetic force • They are the only forces that can both attract and repel.

Electric Forces • Act between charged objects such as protons and electrons.

Magnetic Forces • Act on certain metals, on the poles of magnets, and on moving charges.

Nuclear Forces • Two forces – the strong nuclear force and the weak nuclear force act within the nucleus to hold it together.

2 Strong Nuclear Force • Powerful force of attraction that only acts on the neutrons and protons in the nucleus. • Prevents it from falling apart • Extremely short distances

3 Weak Nuclear Force • Also helps to hold the nucleus together. • Works over shorter ranges than the strong force • 10 -18 m

4 Gravitational Forces • Gravitational force is an attractive force that acts between any two masses. • Every object in the universe attracts every other object

Gravity acts over Large Distances • Fg = G ma mb/r 2. • The greater the masses the greater the gravity • Decreases with distance • Most effective force over distances

The Earth, Moon, and Tides • The moon’s gravity is responsible for the tides on earth.