Force

Definition

A force is any interaction that, when unopposed, changes the motion of an object. It is a vector quantity, having both magnitude and direction.

5 Must Know Facts For Your Next Test

1. The SI unit of force is the newton (N), which is equivalent to $kg \cdot m/s^2$.
2. Newton's First Law states that an object will remain at rest or in uniform motion unless acted upon by a net external force.
3. Newton's Second Law states that the acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass ($F = ma$).
4. Newton's Third Law states that for every action, there is an equal and opposite reaction.
5. Forces can be classified as contact forces (e.g., friction, tension) or field forces (e.g., gravitational, electromagnetic).

Review Questions

• What are the SI units of force?
• How does Newton's Second Law relate force, mass, and acceleration?
• Can you provide examples of contact forces and field forces?

Related terms

Newton's First Law:

An object will remain at rest or in uniform motion unless acted upon by a net external force.

Newton's Second Law:

$F = ma$, where $F$ is force, $m$ is mass, and $a$ is acceleration.

Newton's Third Law:

For every action, there is an equal and opposite reaction.