Physics Crash Course

Sound Waves

The Gist When an object or substance vibrates, it produces sound. These sound waves can only travel through a solid, liquid or gas. They cannot travel through empty space.

Longitudinal Waves Sound waves are longitudinal waves - the vibrations are in the same direction as the direction of travel. Think of a slinky

Words to know the amplitude is the maximum height of the wave from its resting position – the greater the amplitude, the louder the sound the wavelength is the distance between the crests (tops) of two waves next to each other (or any other two identical point on waves next to each other) the frequency is the number of waves per second – the higher the frequency, the closer together the waves are and the higher the pitch

Question 1: Which two diagrams have the same wavelength? Question 2: Which two diagrams have the same frequency? Question 3: Which diagram will have a higher frequency? Question 4: Which diagram will have a higher pitch? Question 5: Which diagram shows a sound that is the loudest?

Light

Non luminous objects A non luminous object (Like a planet) can be seen because light is reflecting off of it.

Color R- Red O- Orange Y- Yellow G- Green B- Blue I- Indigo V- Violet White light is a mixture of many different colours, each with a different frequency. White light can be split up into a spectrum of these colours using a prism, a triangular block of glass or Perspex. Light is refracted when it enters the prism, and each colour is refracted by a different amount. This means that the light leaving the prism is spread out into its different colours, a process called dispersion.

Color Continued There are three primary colours in light: red, green and blue. Light in these colours can be added together to make the secondary colours magenta, cyan and yellow. All three primary colours add together make white light

When light hits a surface, some of it is absorbed and some of it is reflected. The light that is reflected is the colour of the object in that light. For example, a blue object absorbs all the colours of the spectrum except blue: it reflects blue light. Objects appear black in white light because they absorb all colours and reflect none. Objects also appear black in any single colour of light if their colour is not the same as the light. For example, a green object appears black in any other light than green (or white which contains green) because there is no green light shining on it to reflect into your eyes.

Circuits

Series & parallel circuits There are two types of circuit we can make, called series and parallel. The components in a circuit are joined by wires. if there are no branches then it's a series circuit if there are branches it's a parallel circuit

If you follow the circuit diagram from one side of the cell to the other, you should pass through all the different components, one after the other, without any branches. Draw both diagrams in your notebook. Label which symbol represents a lightbulb? A battery?

Series Circuit If you put more lamps into a series circuit, the lamps will be dimmer than before. In a series circuit, if a lamp breaks or a component is disconnected, the circuit is broken and all the components stop working. Series circuits are useful if you want a warning that one of the components in the circuit has failed. They also use less wiring than parallel circuits.

Parallel Circuit In parallel circuits different components are connected on different branches of the wire. If you follow the circuit diagram from one side of the cell to the other, you can only pass through all the different components if you follow all the branches.

Parallel Circuit In a parallel circuit, if a lamp breaks or a component is disconnected from one parallel wire, the components on different branches keep working. And, unlike a series circuit, the lamps stay bright if you add more lamps in parallel. Parallel circuits are useful if you want everything to work, even if one component has failed. This is why our homes are wired up with parallel circuits.

Current & Measuring Current A device called an ammeter is used to measure current. Some types of ammeter have a pointer on a dial, but most have a digital readout. To measure the current flowing through a component in a circuit, you must connect the ammeter in series with it. Current is a measure of how much electric charge flows through a circuit. The more charge that flows, the bigger the current. Current is measured in units called amps. The symbol for amps is A. For example, 20A is a bigger current than 5A.

Pressure

Magnetic Field force lines

Pressure Intro https://www.youtube.com/watch?v=hG7lGZqWFpM https://www.youtube.com/watch?v=vo2iE94iAoA

Calculating Pressure To calculate pressure, you need to know two things: the force or weight exerted the surface area over which the force or weight is spread Pressure is calculated using this equation: pressure = force ÷ area

Example A force of 20 N acts over an area of 4 m2. Calculate the pressure. The force is 20N The area is 4m2 20/4= 5 The units are N/m2 Notice that the unit of pressure here is N/m2 (newtons per square metre). Sometimes you will see another unit being used. This is called the pascal and it has the symbol Pa. 1 Pa = 1 N/m2, so in the example above the pressure is 5 Pa.