A Level Pearson Edexcel Physics Topic 1 Working as a Physicist

SI units for Mass

Kilograms (kg)

Si units for Length

Metre (m)

SI units for Time

Seconds (s)

SI units for Current

Ampere (A)

SI units for Temperature

Kelvin (K)

SI units for Amount of substance

Mole (mol)

SI units for Luminous intensity (brightness of light)

Candela (cd)

Define derived quantities

Derived quantities are physical quantities obtained from combining basic quantities (so the SI units) (such as length, mass, time, etc.) through mathematical relationships.

An example: Show how to get the base SI units for force

As F = ma

and SI units for m = kg and a = ms^-2

so F = kg * ms^-2

therefore SI units for force is kgms^-2

List the ten prefixes

• Tera

• Giga

• Mega

• Kilo

• Centi

• Mili

• Micro

• Nano

• Pico

• Femto

List the symbol for Tera

T

What is the multiplier for Tera (T)

10^12

List the symbol for Giga

G

What is the multiplier for Giga (G)

10^9

What is the symbol for Mega

M

What is the multiplier for Mega (M)

10^6

What is the symbol for Kilo

k

What is the multiplier for Kilo (k)

10³

What is the symbol for Centi

c

What is the multiplier for Centi (c)

10^-2

What is the symbol for Milli

m

What is the multiplier for Milli (m)

10^-3

What is the symbol for Micro

µ

What is the multiplier for Micro (µ)

10^-6

What is the symbol for Nano

n

What is the multiplier for Nano (n)

10^-9

What is the symbol for Pico

p

What is the multiplier for Pico (p)

10^-12

What is the symbol for Femto

f

What is the multiplier for Femto (f)

10^-15

What is Estimation

A skill used to approximate the values of physical quantities, in order to make comparisons, or to check whether the calculated value is reasonable

What is a Random error

It affects precision, meaning they cause differences in measurements which causes a spread out of the mean

What are three ways to reduce random errors

• Take at least 3 repeats and calculate a mean, this allows anomalies to be identified.

• Use computers/ data logger/ cameras to reduce human error and enable smaller intervals

• Use appropriate equipment (e.g. micrometre has a higher resolution (0.1 mm) than a ruler (1mm))

What is a Systematic error

Affects the accuracy, and occur due to the apparatus or faults in the experimental method. These errors cause the results to be to high or to low by the same amount each time.

Two examples of systematic errors

• Zero error (e.g. a balance that hasn’t been zeroed correctly)

• Parallax error (e.g. reading a scale/ruler at a different angle)

Three ways to reduce Systematic errors

• Calibrate the apparats, by measuring the weight of a know value such as a 1kg mass onto the mass balance

• Measure the background radiation beforehand and then excluding it from the final results (if doing radiation experiment)

• Read the central curve on the surface of a liquid (meniscus) at eye level to reduce parallax error and use controls in experiment

What is an uncertainty

An estimate of the difference between a measurement reading and the true value (e.g 20 +-2)

What is Absolute uncertainty

An uncertainty given as a fixed quantity e.g 7 +- 0.6

What is Percentage uncertainty

An uncertainty as a percentage of the measurement 7+- 8.6%

How can we reduce Percentage uncertainty

You can measure larger quantities