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Contact force

A force that acts when two objects touch.

Non-contact force

A force that acts between objects without touching.

Gravitational force

A non-contact force of attraction between objects with mass.

How do we experience Earth's gravitational attraction?

As weight.

Weight formula

W = mg (mass × gravitational field strength).

Spring force

The force a spring exerts when it is stretched or compressed.

Deformation

A change in an object's shape caused by a force.

Weight

The downward force of gravity acting on an object.

Tension

The pulling force carried by a rope, string, or cable.

Surface forces

Forces that occur when two surfaces touch.

What is the perpendicular component of surface force?

Normal force.

What is the parallel component of surface force?

Friction.

Friction term

A force that resists motion between surfaces.

What two things does friction depend on?

The types of surfaces and how hard they press together.

Static friction

Friction that prevents an object from starting to move.

Kinetic friction

Friction between surfaces that are sliding past each other.

Centripetal force

A force directed toward the center that keeps an object moving in a circular path.

Gravity

The force of attraction between objects with mass.

Newton's Law of Universal Gravitation

Every object with mass attracts every other object with mass.

Universal gravitation formula

F = G(m₁m₂)/r²

What does G represent in the universal gravitation formula?

The universal gravitational constant.

What do m₁ and m₂ represent?

The masses of the two objects.

What does r represent in the universal gravitation formula?

The distance between the centers of the two objects.

Inverse square law

A relationship where force decreases by the square of the distance.

Example of the inverse square law

A spray paint can: the spray spreads out as it travels farther away.

Electrostatics

The study of electric charges at rest.

Electric charge

A property of matter that causes it to experience electric forces.

Coulomb's law

The law describing the electric force between charged objects.

Coulomb's law formula

F = k(q₁q₂)/r²

What does k represent in Coulomb's law?

Coulomb's constant.

What do q₁ and q₂ represent in Coulomb's law?

The electric charges of the two objects.

What does r represent in Coulomb's law?

The distance between the two charges.

Magnet

An object that produces a magnetic field and attracts certain materials, such as iron.