Forces

Force

A push or a pull on an object with mass, which causes it to change velocity, measured in Newtons.

Friction

The force that opposes motion, e.g. rough roads or a carpet create a lot of friction as their surface is not smooth

Tension

The force that is acting through a stretched object

Upthrust

This is the force, pushing up on an object in fluid (gas or liquid) due to its mass/density

Magnetic force

The force caused by moving charged particles or aligning domains

Electrostatic force

The force acting between two charged particles

Gravitational force

This is the force that pulls on an object towards the center of the Earth

Air resistance/drag

The force caused by air pushing on an object

Effect of forces

Pushing, pulling, stretching, tearing, bending, squeezing

(By changing the magnitude and direction) Forces can change:

The speed/acceleration of an object

Direction of movement of an object

Shape of an object

What type of quantity is force?

Force is a vector quantity meaning it has magnitude, direction and unit.

Scalar

Quantity with magnitude and unit.

Contact force

A contact force is a force which acts on an object coming physically in contact with it, for example friction.

Non-contact force

A non-contact force is a force which act on an object without coming physically in contact with it, for example, the force of gravity.

Free body diagram

A diagram of an object representing the relative magnitude and direction of all forces acting upon that object in a given situation.

Resultant force

The total amount of force acting on an object or body, along with the direction of the body. The resultant force is zero when the object is at rest, or it is traveling within a uniform velocity throughout (the force is the same in opposite directions).

Hooke’s law

Or the law of elasticity, states that when an object has a relatively small deformation, the size of deformation is directly proportional to the deforming load of force.

Limit of elasticity

The point beyond which the material you are stretching, becomes permanently stretched.

Limit of proportion

The point beyond which Hooke’s law is no longer true when stretching and material.

Stopping distance

Breaking distance + thinking distance

Thinking distance

The distance it takes a person to react and make up their mind before stopping

What affects thinking distance?

Substances, state of mind, surrounding environment, distractions, tiredness, car speed

Breaking distance

The distance that the vehicle has traveled after pressing the brakes

what affects breaking distance?

Condition of the road, condition of the brakes and tires, mass of the car, speed of the car

Newtons first law

The velocity of a body remains constant until the body is acting upon by an external force

Newtons second law

The acceleration of a body is parallel and directly proportional to the resultant force and inversely proportional to the mass

Newtons third law

The mutual forces of action and reaction between two bodies are equal opposite and collinear

Net force

The combined effect of all the pushing, and pulling forces actually acting on the object. If the forces pushing or pulling on an object are not balanced (a net force acts), then the object will accelerate in the direction of the net force.