Physics definition - Unit 1

Force

A push or a pull which one object applies on another. The force can act from a distance (gravity), or it may be contact force (Friction)

What can a force do?

• Change the shape of the object

• Change the speed of an object

• Change the direction of motion of an object

Mass

Amount of matter in an object and is measured in kilograms(kg)

Weight

A force due to the pull of gravity on the object; and on the earth the pull of gravity is 10N on a mass of 1kg

Hooke’s Law

The extension of a spring is directly proportional to the force applied, provided that the limit of proportionality is not exceeded

Principle of moments

At equilibrium the sum of the clockwise moments equals the sum of the anticlockwise moments about a pivot

Moment

turning effect of a force

Centre of gravity

The point on an object where all of the weight/mass appears

Vectors

A quantity that does depend on directions

• Velocity

• displacement

• acceleration

Scalars

A quantity that does not depend on directions

• speed

• distance

• Rate of change of speed

Newton’s 1st law

Objects at rest tends to remain at rest, while moving objects continue to move at uniform speed in a straight line - unless acted upon by an unbalanced force

Newton’s 2nd law

A resultant force will cause on object to accelerate and that the acceleration is proportional to the size of the resultant force

A newton

is the force that will give a mass of 1kg an acceleration of 1m/s^2

Radioactive

When an unstable neucleus admits radiation in order to become more stable

Alpha particles

helium nuclei consisting of 2 protons and 2 neutrons

Beta Particles

Fast electrons

Gamma Radiation

An electromagnetic was of high energy

Half-life

The time taken for half of the nuclei now present to decay - never gets to zero

Nuclear Fission

When a heavy nucleus splits into two smaller nuclei releasing a large amount of energy

Nuclear Fusion

When two light nucle join or combine together to produce a heavy nucleus, releasing large amount of energy

Energy

Enables physical work to be done

Forms of Energy

• chemical

• thermol

• light

• sound

• electrical (and magnectic)

• nuclear

• protential (Elastic and gravitational)

• kinetic

Law of conservation of energy

Energy cannot be created or destoryed, but it can transfer from one form to another. The total amount of energy does not change

Renewable

Can be replaced within a human lifetime

Work

The useful energy output of any energy transfer. Physical work is done when something moves against a force nnn

Power

The rate of transfer of energy/ The rate of work done

Watt

Joule(s) per second