NCEA Level 1 Science/Physical inquiry and physics concepts

Simple pulley system

Introduction

Energy is the capacity to do work. It is needed to make things move or change. Objects can have many forms of energy at the same time and all living things require energy. Energy exists in many different forms and can change from one form to another. It is not a substance, it can't be weighed and doesn't take up space. It is a cause or agent of change.

There are two types of energy:

• active
• potential

Active Energy

Active Energy are forms of energy which can be detected when particles move or objects move and it's effects can be seen. These include:

• Light Energy - The light makes it possible to see things when it bounces of objects and enters your eye. Some chemicals and living organisms such as a firefly may give of light(a light source). Light Energy moves through space as a wave.
• Heat Energy - Causes Particles in a substance to move faster (hotter the particles, faster the movement) and space out, becoming less dense. This change in density may lead to thermal expansion or even a change of state.
• Electrical Energy - is energy carried by charged electrons, moving through a conductor. There must be an electrical force field to provide enough force to drive around a circuit.
• Sound Energy - objects that vibrate cause sound energy to travel through air as waves, called sound waves. Sound waves travel at different speeds depending on the material it is passing through.
• Kinetic Energy - The energy of a moving object. The amount of kinetic energy an object has depends on the mass and the speed of the object.The formula for energy is E_k=¹/₂mv²

Potential Energy

Potential Energy is stored energy can only be detected when it is transformed into an active energy.

• Chemical Potential Energy - is stored in food and fuel. It is released when the food is burnt up by respiration and when fuel is burned.
• Magnetic Potential Energy - is stored in a magnetic material (iron,cobalt,nickel)that has been moved away from a magnet. It is released when the material moves towards the magnet.
• Gravitational Potential Energy - is stored in object above ground. Amount of gravitational potential energy possessed by an object depends on the height of the object above ground. It is released when object moves back to ground.
• Nuclear Potential Energy - Stored in the nucleus of an atom. Released when nucleus splits or joins to another nucleus.

Energy Changes

Energy changes occur when:

• Energy is transferred from one object to another.
• Energy is transformed into various other forms.

Mechanics

In general terms motion can be defined as a change in one specific property using another property as point of reference (time can be the best point of reference).

In space or area (3d or 2d) motion can be defined as the position changes experimented on it's position coordinates.

Ex: A car was parked on a sleeve 10cm from a rock but later the owner saw the car moved 50cm from the same rock. In this case the car experimented motion because changed its position from 10cm from the rock to 50cm.

Electricity

Direction of flow of electric current in a circuit

EfieldTwoOppositePointCharges.svgIllustration of the electric vectorfield surrounding two opposite point charges. Red is positive, green is negative.

Electric field lines emanating from a point positive charge suspended over a negatively-charged infinite sheet

Electric current is the flow of electric charge. The symbol for electric current is 'I' and unit is ampere (A).

The direction of the conventional current is the direction of a small positive charge, should it be able to move. Positive charges exert an outwards force while negative charges exert an inwards force. Should protons be able to move, they would move towards the negative end of the terminal.

One Coulomb is equal to 6x10¹⁸ electrons. One Coulomb is equal to an amp. An ammeter can be used to measure the current in a circuit.

Heat

Heat energy (also known as Thermal Energy) is the total kinetic energy of the particles in a material. Particles move around or vibrate faster as an object heats up.

Heat energy can be transformed into mechanical energy using an engine (for example, a steam engine)

Many energy transformations/transfers result in some heat energy being given out. For example, striking a bell with a hammer transforms kinetic energy in the hammer into sound energy in the air, but also into a small amount of heat energy in the bell.

Heat energy is not the same as temperature. Temperature is, roughly speaking, proportional to the average energy of the particles in a material, whereas heat energy is the Total kinetic energy of the particles. Nonetheless, we can say that the temperature is "how hot something is".