The Laws of Motion

There are three laws of motion that describe the relationship between forces, mass, and acceleration.

Force is any influence that causes an object to change, either concerning its movement, direction, or geometrical construction.

Mass is a physical property of matter that depends on size and shape of matter, and is expressed as kilograms by the SI system.

Newton’s first law of motion describes inertia. According to this law, a body at rest tends to stay at rest, and a body in motion tends to stay in motion, unless acted on by a net external force.

The second law states that the net force on an object is equal to the rate of change, or derivative, of its linear momentum.

The third law of motion states that for every action, there is an equal and opposite reaction.

Weight is taken as the force on an object due to gravity, and is different than the mass of an object.

The normal force comes about when an object contacts a surface; the resulting force is always perpendicular to the surface of contact.

Basic problem-solving techniques can aid in the solution of problems involving motion (i.e., the laws of motion).

Forces act in a particular direction and have sizes dependent upon how strong the push or pull is.

Net force affects the motion, postion and/or shape of objects (some important and commonly used forces are friction, drag and deformation).

If two systems are in contact and moving relative to one another, then the friction between them is called kinetic friction.

Static friction is a type of friction that occurs to resist motion when two objects are at rest against each other.

Combining motion on inclines with friction uses such concepts as equilibrium and contact force on an incline.

The drag force is the resistive force felt by objects moving through fluids and is proportional to the square of the object's speed.

The ratio of force to area $\frac{F}{A}$ is called stress and the ratio of change in length to length $\frac{\Delta L}{L}$ is called the strain.

An object is said to be in equilibrium when there is no external net force acting on it.

Forces can be transferred from one object to another through connections.

An object in circular motion undergoes acceleration due to centripetal force in the direction of the center of rotation.