Level 1 Physical Science: Linear Relationships Flashcards
What is a variable
Things that you can change during an investigation.
What are the 3 main variables
1) Independent variable
2) Dependent variable
3) Controlled variable
What is a Independent variable (IMPORTANT)
This is the variable that you choose to change within a set range of values, for example changing the distance measured
What is a dependent variable (IMPORTANT)
This variable ‘depends’ on the independent variable. For example, the time it takes to run different distances
What is a controlled variable (IMPORTANT)
These are all the other possible things that could change in an investigation but you are not testing. These need to be controlled, i.e. not change during the experiment. For example, in the above examples (distances, and time taken to run those distances) controlled variables would be the person running, where they are running, the shoes they wear, the weather conditions.
What is the independent variable for the investigation: the relationship between force on a spring and how far the spring extends
Independent variable= Force on the spring
What is the dependent variable for the investigation: the relationship between force on a spring and how far the spring extends
Dependent variable= extension of the spring
What are the control variables for the investigation: the relationship between force on a spring and how far the spring extends
The spring used, ruler used to measure, where the extension is measured from.
What is the independent variable for the investigation: the relationship between the drop height of a ball and the height it bounces back up to
the drop height of the ball
What is the dependent variable for the investigation: the relationship between the drop height of a ball and the height it bounces back up to
the bounce back height
What are the control variables for the investigation: the relationship between the drop height of a ball and the height it bounces back up to
the person dropping, the ball, the ball used, the place the ball is dropped
Ethan was told by his teacher to find the relationship between the mass of a ball and how high it can bounce. What is the independent variable
Mass of ball
How many different variables do we need to do in our investigation
At least 5
To measure mass what would the equipment be and what are the units
Electronic scales. Units= Kilograms, kg or Grams, g
To measure distance what would the equipment be and what are the units
Ruler or metre ruler. Units= Millimetres, mm or Centimetres, cm or Metres, m
To measure temperature what would the equipment be and what are the units
Thermometer. Units= Degrees Celsius, °C
To measure Time what would the equipment be and what are the units
Stopwatch. Units= Seconds, s
To increase the accuracy of your measurements, you should repeat (do trials of) your measurements ____ times. And then average them.
To increase the accuracy of your measurements you should repeat (do 3 trials of) your measurements 3 times. And then average them.
How many variables do you need to do and how many times do you measure each one? (repeats/trials)
You must do at least 5 variables and repeat each one 3 times.
What are the 2 errors you need to be aware of that can affect your accuracy of your measurements
1) Zero error
2) Parallax error
What is Zero error
Some measuring equipment (such as rulers) does not start at zero when it should. We call this ZERO ERROR. You need to check for this before using your equipment.
What is Parallax error
If you look at a measurement from above or below the reading you will get the wrong value. You must take measurements at EYE LEVEL to avoid this error.
What are the 9 rules for drawing a straight line graph
1) Use a RULER
2) Your graph should take up at least HALF A PAGE
3) The INDEPENDENT VARIABLE goes on the X AXIS (horizontal axis)
4) The DEPENDENT VARIABLE goes on the Y AXIS (vertical axis)
5) The SCALE on any axis must be EVEN ie. It goes up in even intervals eg 0,2,4
6) Plot POINTS with a CROSS
7) LABEL each axis with the VARIABLE AND ITS UNIT
8) Draw a LINE OF BEST FIT through our points (this is not join the dots but draw a line to show the general shape of the points).
9) Give the graph a TITLE that has both the INDEPENDENT AND DEPENDENT VARIABLE in it.
What axis on the graph does the independent variable go on
The x axis (horizontal axis)
What axis on the graph does the dependent variable go on
The y axis (vertical axis)
What is very important for working out the relationship between the independent and dependent variables
The steepness of a straight line graph you have drawn is very important when working out the relationship between the independent and dependent variable you are investigating.
In physics we always work out a number value for the steepness called the ___________
In physics we always work out a number value for the steepness called the GRADIENT
What is the equation for calculating the gradient of a line
GRADIENT= rise/run
How do we use the GRADIENT= rise/run equation
To use this equation you need to choose two points which are on your line, (not the actual points marked with a cross).
What is the final thing we need to do to find the relationship between two variables
To find the relationship between two variables the final thing you need to do is work out the linear equation that is shown by your line of best fit. For graphs to go through (0,0) the basic equation is: y=mx(+c)
What is the y in the equation y=mx+c)
the vertical axis (y), the dependent variable
What is the m in the equation y=mx+c
the gradient
What is the x in the equation y=mx+c
horizontal axis (x), independent variable
What is the +c in the equation y=mx+c
the y intercept (where the graph meets the y axis
What do you use when substituting your findings into the equation y=mx+c
The symbols of the variables NOT the units!!
What would you write if the symbol for the dependent variable was d, the symbol for the independent variable was t, the gradient was 2 and the y intercept was 1.6
d=2t+1.6
To get the achieved mark for the independent variable what are the 3 things you must do
1) The independent variable must be correct
2) There must be at least 5 different values used, with unit given
3) There must be a reasonable range
To get the achieved mark for the dependent variable what are the 3 things you must do
1) The dependent variable must be correct
2) The values are measured, units given
3) The measured values have acceptable accuracy
To get the merit mark for the control variables what are the 2 things you must do
1) One valid variable must be identified
2) They must be correctly described
To get the merit mark for the accuracy improving what are the 2 things you must do
1) One valid technique must be used
2) It must be correctly processed
To get the achieved mark for method what do you have to do
Give a reasonable description of what was doen
To get the 3 achieved and 2 merit marks for graph what are the 5 things you must do
1) Axes must be labelled with variable name and unit
2) Scales/graph size appropriate
3) Points plotted accurately
4) Graph line relevant to plotted points
5) Graph line straight and accurate
To get the 2 merit marks for gradient what are the 2 things you must do
1) Correct method used
2) Correct value/ reasonable sig fig
To get the 1 achieved and 1 merit mark for conclusion what are the 2 things you must do
1) Have correct description of type of relationship
2) have the correct equation
To get the excellence mark for discussion what are the 5 things you must do
1) Independent variable range
2) controlled variable
3) accuracy improving
4) difficulties/issues
5) physics ideas
What are the 2 things the exam is going to be about
1) Newtons laws
2) Mechanics (forces)
What is forces
Forces can be a PUSH or PULL and will cause the motion of an object
What is the symbol and units for Forces
Symbol F, measured in NEWTONS, N
What can we represent forces with
arrows called VECTORS. A VECTOR has MAGNITUDE (length tells you size) and DIRECTION.
What are the 7 different forces
1) Force of gravity, weight (Fg)
2) Support/Reaction (at 90° to the surface)
3) Friction (opposes motion) between 2 surfaces
4) Air resistance/Drag (opposite direction to motion)
5) Thrust (from engines)
6) Lift (planes, helicopters) upward
7) Tension (ropes/strings) in BOTH directions
How many laws does Newton have
2
What is Newtons first law
NEWTONS FIRST LAW: If the forces on on object are BALANCED the NET FORCE IS ZERO and the object will remain STATIONARY or at CONSTANT SPEED
What is Newtons second law
NEWTONS SECOND LAW: If the forced on an object are UNBALANCED the NET FORCE is NOT ZERO and the object will ACCELERATE
What is Fnet
Net force
If a NET FORCE acts on an object it will ACCELERATE in the same direction what is the formula for this?
Fnet=ma
What is Mass
Mass is determined by the number of particles/matter measured in (kg)
What is Weight or force of gravity
Weight or force of gravity is a downwards force measured in newtons (N)
What is Pressure
Pressure is a force over a surface area. Pressure has symbol, P, and is measured in Pascal (symbol Pa) or Nm−²
What are the key points to remember for the exam
1) Aim: find the relationship between a & b (highlight the aim in the eXAM)
What is important to remember for independent variable (what you change)
Its what you change.
1) Range (minimum to maximum possible with equipment) eg 1m,3m,5m,7m,9m
2) 4-5 settings a or b
3) units
What is important to remember for dependent variable (what you measure)
Its what you measure.
1) How are you going to MEASURE this and INCREASE ACCURACY
2) zero error
3) parallax error
4) repeating and calculating average
5) outliers
You need to justify your choices for these 5 things in your conclusion
What is important to remember for control variables
1) what might cause a change in the dependent variable
2) how can you control the variable
When calculating gradient what do you use
always use the graph to calculate gradient
What is the relationship
y=mx+c
Processing data on the Graph 6 key things to remember
1) use graph paper!!
2) which variable to plot on each axis (dependent, y) and (independent, x)
3) decide on a scale, (both should start form 0) graph should be at least 1/2 width and 1/2 height of graph paper. Scale should be easy to read at any gridline
4) label each axis with a or b (unit)
5) plot each point as a neat cross (sharp pencil)
6) line of best fit
