There are four fundamental interactions/forces in nature: gravitation, electromagnetism, strong nuclear and weak nuclear forces. All phenomena are due to the presence of one or more of these interactions. Forces act on objects and can act at a distance through respective physical field, causing a change in motion or in the state of matter.

Version for ages 12 to 15

Gravity and electromagnetism are the two forces whose effects are most evident to us. These two forces are responsible for the majority of motions in the universe. The motion of an object depends on how a force acts on it.

Version for ages 9 to 12

When a force acts on an object it can change its shape or its state of motion. We cannot see forces but we can understand them by their effects. An object can have an effect on another through a force, either by being in contact with it or from a distance. There is a limited number of forces in our universe.


Breaking down of the Fundamental Forces Big Idea of Science

Intermediate ideas of Science Small Ideas of Science

Types of interactions

There are only four forms of interactions: gravity, electromagnetism, the strong nuclear interaction and the weak nuclear interaction. Every motion or change of states is due to one or more of these interactions. The effects of these interactions can be observed in all scales of the universe.

Forces and motion

When a force (or more) acts on an object, the object will either change its kinetic state or shape. Depending on the size and the direction of the total force the object can perform different types of motions. For objects with speeds much smaller than the speed of light, the way forces act on objects is described by Newton’s laws. For objects with speeds close to the speed of light, the way forces act on objects is described by Einstein’s General theory of relativity.