(it's so much easier on the eyes)

Year 9 2019 Half Yearly Science Exam Notes by Aaron Lacambra (study with textbook in hand)

Credit to Rizelle for sending this to me because I cant write with a broken wrist, but I can still type so lucky you



1. Newtons 3 laws:
i) any object that is uniform (not moving) will remain uniform unless an external force acts on it (known as law of inertia)
ii) force = mass x acceleration
iii) for every action there is an equal and opposite reaction

2. Word definitions:
i) Gravity: the force that attracts a body to the centre of the earth, or any other physical body containing mass
ii) Acceleration: rate of change in speed
iii) Thrust: a forward push

3. Why do we have airbags in cars?
The purpose of an airbag is to reduce the speed in which the driver/passengers collide with the car in attempt to minimise the chance of injury or harm to the driver/passengers.

4. What are crumple zones for (in cars)
A part of a motor vehicle (especially in the front and back) designed to easily crumple easily during a crash to absorb and maintain the force of an impact.

5. What is inertia?
Inertia is the resistance of an object in changing its motion or direction. An object will continue to move at the same speed unless acted upon by an external, unbalanced force. Example: A ball is rolling on the floor. The ball slows down eventually because its motion is acted upon by the friction of the floor, causing it to inevitably stop.

6. Which of newtons laws affect a deflating balloon? (While you are studying this search up the answer to question 17)
As the balloon deflates, gas is being expelled from inside the balloon into the air and the ground. According to newtons 3rd law of motion, for every action there is an equal and opposite reaction. Because the gas is exerting force from inside the balloon, the balloon is being propelled forward into the air. As a result, the balloon is being propelled by the opposing force.

7. Acceleration and resistance difference (How does one affect the other)
All things are in motion unless acted upon by external force. For something to be in motion, it probably would have been still at one point and at another point began to accelerate. One common thing that stops the perpetual movement of an object or whatever it is is resistance. An example of resistance is a ball moving forward. If it rolls on the floor, it creates friction as it moves, releasing heat which is energy and it will inevitably stop the ball. A car travelling at a high speed on the M4 would inevitably slow down due to 3 factors that I can think of at the moment, friction, gravity and wind resistance. Friction from the wheels and the road would stop the car. Gravity would force the car to create more contact with the road and wind resistance would act as an external force that stops the car from maintaining speed and moving forward.

8. How do we measure an instantaneous speed?
Speed = Distance (over) time // s = d/t (formula)


9. Different kinds of light radiation for increasing frequency? (not sure I guessed this)
Microwaves, radio waves, infrared rays, ultraviolet, visible light, gamma rays and x-rays???

10. Draw a diagram for compression and rarefaction
Refer to page 124-125

11. Diagrams to show how light reflects on a convex and concave mirror (include focal point)
The answer is the diagrams you did in investigation 4.6. If you didn’t do that investigation, I don’t think I did it, refer to page 134.

12. Give 2 uses for kinds of radiation
i) x-rays: can show shadow-like images of bones are organs, used for determining injury or disease.
ii) ultraviolet light (UV light): can be used to sterilise surgery equipment and ait in operating rooms.

13. Label the diagram of the eye
(from what I think there was in the topic test): suspensory ligaments, ciliary muscles, iris, lens, pupil, sclera? Refer to page 140

14. Label a diagram of why objects are upside down at the back of the eye
Refer to page 140

15. Diagram to show why an object has certain colours
I can't draw diagrams here; I think page 146 is good. I'd look this up if I were you. I recommend reading page 143-144 for an explanation.

16. Distance and displacement. Math Pythagoras Theorem:
a square = c square − b square
b square = c square − a square
c square = a square + b square
(if you don't understand this don't waste your time, either learn this or go study another question)

17. Draw a diagram to explain how a balloon moves while it is deflating
Draw a picture of a balloon deflating. Show gas leaving and use arrows to show that the gas is pushing the balloon forward in opposition (newtons 3rd law). Wherever the gas pushes the balloon in your diagram, make the balloon go the opposite direction.

18. Draw a diagram to explain how a ball moves in the backseat of a car while it is moving
Draw a picture of the car going forward with the ball going backwards, use arrows. Do this for left, right, front and back.

19. Interpreting a graph about acceleration
Force (times) mass = acceleration // f x m = a (formula)

20. Label an ear diagram
For this question you have to label the 6 main parts of the ear accurately;
The middle ear, auricle, semicircular canals, outer ear, ear canal, inner ear, auditory nerve, eustachian tube. (You don't have to do all of them just 6 correctly) refer to page 130-131




1. Can sound travel through empty space? Why?
No. Sound is the vibration of particles in the air from one place to another. In space where it is almost a complete vacuum, there are little to no particles for sound to transfer vibrations to. Because of this, if you were to theoretically scream in space, the sound coming out of your mouth would immediately disappear.

2. What's the word used of how often something happens?

3. What does sound travel best through?
Sound travels best through solids. As mentioned before, sound transfers its vibrations from one particle to another. The more closely compact the particles are, the more efficiently the vibrations travel through one another. If you were sitting at the end of a long dinner table with your mate at the other end and he was to tap on the table repetitively with the bottom of his fork while your ear is pressed against the table, you would be able to hear it. Sound travels best through solids, slower through liquids and slowest through gases.

4. What is the speed of sound through air?
The speed of sound in air is between about 300 m/s and 350 m/s, depending on the temperature. (refer to page 132)

5. What do dolphins use sound for?
It is said that dolphins use echolocation by making clicking sounds and interpreting where something is by the ricochet (bouncing back) of the sound. This helps navigate through the water by essentially, helping them see better in the water. They also use sound to communicate with one another. Dolphins are intelligent animals.

6. What is the difference between radiation, convection and conduction?
Refer to this website for a clearer cleaner explanation. Its easier for the both of us.

7. What is the relationship between the angle of incidents and the angle of reflection?
When light strikes a shiny surface like a mirror, light is reflected from that surface. Light reflected from a mirror follows the law of reflection which states: The angle of incidence = the angle of reflection. (Refer to the diagram in page 132)

8. What is the difference between transparent, translucent and opaque?
Shiny surfaces reflect light but if a surface absorbs light it is said to be opaque. If most of the light travels through a material, the surface is called translucent. Some surfaces allow just enough light to travel though to allow objects to be detected on the other side, but they scatter so much light that the objects are not clearly visible. Frosted glass used in bathroom windows is an example of this. Such materials are said to be translucent. (for images refer to page 134)

9. What kinds of lenses and mirrors have a virtual focal point?
A concave lens and a convex

10. Why does light spread out when it goes through a prism?
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

11. Why does a shirt seem to have a certain colour?
Light receptors within the eye transmit messages to the brain, which produces the familiar sensations of colour. Newton observed that colour is not inherent in objects. Rather, the surface of an object reflects some colours and absorbs all the others. We perceive only the reflected colours

12. Define diverge
Means to refract away. For those who don't know by now, refraction is the bending of light as it passes from one substance to another

13. What are the 2 types of light sensing cells in your retina?
There are two types of light-sensitive elements in the retina: rods and cones

14. What is the speed of light?
The speed of light is 299 792 458 m/s

15. If I put 2 filters together, what happens to the light?
When white light shines on a red filter, all of the colours that form the white light are absorbed except red, which is reflected. Putting 2 filters of different colours together will allow no colour to pass through, so its just nothing. Nothing goes through both filters it's just black

16. Why does the eye change shape?
The pupil changes shape to adjust and allow the optimum amount of light that should enter your eye depending on the brightness of the environment that you are in. Fun fact, pirates used to wear eye patches not just because they always have a missing eye for some oddly cool reason but because below the deck of a boat is pitch black. You cannot really see anything, however the eye that has been convered by the eye patch is adjusted to its environment, that eye is adjusted for the darkness. Pirates switch their eye patch to the other eye when the go below the deck to allow the adjusted eye to view the bottom of the deck instead of the eye that was originally exposed to the bright environment outside

17. What are some uses for electromagnetic radiation
Electromagnets are used in all kinds of electric devices, including hard disk drives, speakers, motors, and generators, as well as in scrap yards to pick up heavy scrap metal. They're even used in MRI machines, which utilize magnets to take photos of your insides


18. Difference between distance and displacement
Distance as defined by the textbook is a scalar measurement of length expressed only as a size, with no direction whereas displacement is the action of moving something from its place or position

19. What is the difference between the vector and the scalar?
A scalar quantity is a one dimensional measurement of quantity such as temperature and mass, the measurement of a singular thing. The difference between the two is that a vector has more than one number associated with it and you can tell the difference between the two because a diagram of a vector usually has a direction associated with it. A vector is a quantity that has both a magnitude and a direction. Vector quantities are important in the study of motion. Some examples of vector quantities include force, velocity, acceleration, displacement, and momentum

20. How do we calculate speed?
Acceleration (over) time = speed // s = a/t (formula)

21. What is the difference between instantaneous speed and average speed?
Instantaneous speed is the exact speed that a body is moving at, at a given instant in time. It is a true measure of the body's motion for that point in time. An average speed tells you how much distance a body covers during a certain time span, but it does not tell you much about the actual motion that occurred

22. Bell times (Not sure why this is a question)
8:10 – Period 0
8:30 – PCG
8:45 – Period 1
9:50 – Period 2
10:55 – Recess
11:15 – Period 3
12:20 – Lunch
1:00 – Period 4
2:05 – Period 5
3:10 – Home time (Highschool)

23. Word definitions:
i) Air resistance: Air resistance is a force that is caused by air. The force acts in the opposite direction to an object moving through the air
ii) Friction: The resistance that one surface or object encounters when moving over another
iii) Thrust: A forward push
iv) Weight: A body's mass or the quantity of matter contained inside of it (the heaviness of a person or thing)

24. State the difference between momentum and inertia
Inertia is a characteristic of the object related to its mass. Inertia tells you how much force it will take to cause a particular acceleration on the object whereas momentum is a function of an object's mass and velocity. Momentum is a measure of the kinetic energy of the object

25. What is the unit used for measuring force?
The unit that is used for measuring force is newtons

26. What is the effect of mass on acceleration?
The acceleration of an object is totally dependant on the opposing force acting upon the mass of the object. Increasing the force tends to increase acceleration whereas increasing mass tends to decrease acceleration. Acceleration is faster on objects that have less mass in comparison to objects with larger masses

End of exam notes