Physical quantity
equivalents
mass 1 Kg 1000g
1g .001kg
distance 1mm 0.001m
1cm 0.01m
1m 1000mm
1000m
1km
These are the “tricky” ones
Pre-fix Multiplier
nano (n) 10-9 .000000001
micro (μ) 10-6 .000001
milli (m) 10-3 .001
kilo (k) 103 1000
mega (M) 106 1000000
giga (G) 109 1000000000
If your quantity (number) has a prefix then you multiply the number part by the value of the prefix to get units.
Example: 120kJ = 120 x 103 = 120,000 J Example: 350 mm = 350 x 10-3 = 0.35 m
If you have a number and you would like to use a prefix then you divide the number by the value of the prefix to get the Number with a Prefix
Example: 120,000J = 120,000 ÷ 103 = 120kJ Example: 0.35m = 0.35 ÷ 10-3 = 350mm
kg (kilogram) is the only SI unit that has a prefix - all the others don’t i.e. A (ampere)J (joule) m (metre)N (newton)s (second)V (volt)W (watt)Ω (ohm)
Divide you page down the middle and labelBefore and After (collision).Draw a diagram!
Write down your formulas
Substitute values: Remember to look for stationary objects - their velocity is zero and that part of the equation goes away!
Now let LHS (before) = RHS (after)Then solve for unknown value (i.e. what the question asked you to find)
Note : the unit of momentum is kgm/s or kgms-1
Note : the formula for momentum is given as p=mv in the Data Booklet
Use “u” for velocity before and use “v” for
velocity after collision
Constant Velocity … (Newton’s 1st Law) Constant Acceleration due to gravity
Draw diagram or sketch
List known and unknown quantities
Draw line down centre of page
On LHS write Horizontal
On RHS write Vertical
t
uva
tvs
Constant Velocity Constant Acceleration
Time (t) is common to both horizontal and vertical motion
Speed orVelocity
(ms-1)
time (s)
acceleration
constant speed
deceleration
deceleration
constant speed
Distance travelled = Area under graph
NOTE: v > u gives acceleration; v < u gives deceleration or negative acceleration
Again, remember that VS= V1 + V2
… you don’t need to use formula 2 twice!
Try to use formula 1 first.You need 3 of the 4 terms V1, V2, R1 or R2.(VS is not required)
Use this formula if you can’t use formula 1. Look for VS in the question.
Before you begin. Remember that VS= V1 + V2
Now write down what you know and don’t know !
The question will indicate whether the temperature (Thermistor) or light (LDR) is increasing or decreasing.Use this information to start your answer e.g “As the light level falls the resistance of the LDR increases …”
The LDR or Thermistor
may be placed here – you need
to think how this affects
step 2
LDR1
R2
Vs
V2
Explain the Science of the LDR (L.U.R.D.) orThermistor (T.U.R.D.)
This could be any output device, e.g. relay, bell, buzzer etc.
Explain How the Transistor works:-Switches ON at the threshold voltage
0.7 V for npn transistor1.0 – 2.0 volts for
MOSFET
Copy this from the Physics data booklet
Read the question carefully and select two of the three terms (ratios)
shown in the formula – you should end up with a simpler relationship
containing two terms (ratios).
Cross multiply to simplify then solve for the unknown term..
Transformers are not 100% efficient due to•Heat loss•Magnetising currents•Sound (vibrations)
Cooling Curve
Temperature(T)
time(t)
Gas
Liquid
SolidWhen material is cooling it gives off heat
energyWhen its temperature is increasing the
material is absorbing heat energy
LED numerical questions are usually worth three marks.
The question usually gives the operational or working voltage of the LED… and the operational or operating current of the LED.Then it asks you to calculate R
Vs
RThe current through R is the same as the operating current of the LED
Remember to include unit Ω
This is where you
get the extra mark
If the question asks you to find a “half life” or “how long a sample takes to decay” or “the initial or final level of Activity” then it’s a good bet that you need a …………..
Activity (units)
Time (units)
Fill in the initial Activity
Fill in the initial Activity
Initial time = 0
Initial time = 0
0
Divide previous
Activity by 2
Divide previous
Activity by 2
Divide previous
Activity by 2
Divide previous
Activity by 2
Until you reach your
Final Activity
Until you reach your
Final Activity
Add one ½ Life to previous time
Add one ½ Life to previous time
Add one ½ Life to previous time
Add one ½ Life to previous time
Until your reach your Final timeUntil your reach your Final time
To find the number of half lives – count the number of entries you have Made in the time row, but don’t count the first one (the zero value).
You will get the Units from the question
To find the Half Life divide the final time by the number of half lives
Initially Vc = Logic 0 (0V)
Not gates inverts Logic to Logic 1 (5v)This is applied to top of R1Capacitor charge up to Logic 1 (5v)
Not gates inverts Logic to Logic 0 (0v)This is applied to top of R1Capacitor discharges to Logic 0 (0v)
The process repeats
R1
Logic 0 = 0VLogic 1 = 5V
Timing/ Frequency determined by R1 and C
½ mark
½ mark
½ mark
½ mark