S1 Physics Notes Flashcards
Define a “scalar” quantity (brackets highlight key points)
A quantity that can be (accurately described) using only its (magnitude) and (units)
Define a “vector” quantity
A quantity that can only be (accurately described) using its (magnitude), (units) and (direction)
What is the difference between distance and displacement?
(Distance) is a (scalar quantity) and (displacement) is the (vector equivalent)
What is the difference between speed and velocity?
(Speed) is a (scalar quantity) and (velocity) is the (vector equivalent)
= speed requires magnitude where velocity requires direction and magnitude
Define velocity and give the units it’s measured in
(Speed) in a (given direction), (metres per second) / (m/s)
Define displacement and give the unit it’s measured in
(Distance) travelled in a (given direction), (metres) / (m)
Apart from direction, what is the other difference between scalar and vector quantities?
(Scalars) (cannot) have (negative units), whereas (vectors) (can) have (negative units)
What is a negative unit used to express?
(Backwards movement) (relative) to the (starting point)
Define constant speed/velocity
(Moving) at a (steady/constant rate)
Define uniform acceleration
When speed/velocity is increasing or decreasing a constant rate
Define acceleration and the give the units it’s measured in
(Change) in (velocity) over (unit time), (metres per second squared) / (m/s2)
What is a ticker tape timer and how does it work?
A (ticker tape timer) is a device that (stamps a strip of ticker tape) with a dot (many times a second). This can be used to analyse motion by looking at the (frequency of the dots). The (farther apart) the dots are the (faster) the object is (moving). We can use this data to (calculate speed) by taking the (distance between 2 dots) and (dividing) it by the (frequency of the dots), i.e. (5 dots per second/1 dot per 0.2 seconds). For example: (1cm/0.2s = [5cm/s])
What does the gradient of a displacement/time graph represent?
(Speed/velocity)
What does the gradient of a velocity/time graph represent?
(Acceleration)
What does a curve on d/t graph represent?
Acceleration (represented by upward curve) / deceleration (downward curve)
What does a curve on a v/t graph represent?
(Non-constant) acceleration/decelerartion
What does the area under the gradient of a v/t graph represent?
(Displacement)
What do the variables s, u, v, a and t represent in an equation?
s = displacement
u = initial velocity
v = final velocity
a = acceleration
t = time
What is the equation for average velocity?
v = u +at
OR
v = d/t
Equations for distance
s = (u+v)t / 2
s = ut + 1/2 at2
s = v/t
Equation for final velocity
v2= u2 + 2as
Or
v= u + at
Or the rearranged equation from
S= ut + 1/2at2
What is Newton’s First Law of motion?
A body will remain at rest or travel at a constant speed unless compelled to change by an external force
What is inertia?
(Reluctance) to (start moving) when at (rest) or (reluctance) to (stop moving) when in (motion)
What 2 physical states can an object be in when the forces acting on it are balanced?
(Stationary) / (moving at constant speed)
What is Newton’s Second Law?
The resultant force produced is directly proportional to the acceleration and inversely proportional to the mass
F = ma
How else can Newton’s second law be written (equation)?
F = ma
What is Newton’s Third Law?
If (body A) exerts a (force) on (body B) then (body B) will exert a (force) on (body A) that is (equal in magnitude) but (opposite in direction)
What effects can forces have on objects (3)
They cause a change in the
1. motion,
2. size, or
3. shape of a body
What is the difference between mass and weight?
(Mass) is (unchanging) and is measured in (kilograms/kg), whereas (weight) is the (effect of gravity) on an object’s (mass) and is measured in (Newtons/N)
What is Hooke’s Law? (Give definition, formula and units)
The extension of a spring is proportional to the stretching force so long as the spring is not permanently stretched
F = kx
F
K x
= N=N/m x m
(Spring force = spring constant x extension)
What apparatus is used to measure weight?
(Newton Spring Balance)
Define “pressure”
The (force) acting on (unit area)
Give the formula and the SI unit for pressure
P = F/A
N/m2 / Pa
1N/m2 = 1Pa
Pa
What 2 principles do hydraulic machines work on (Hydraulic principle)
Liquids are incompressible
Pressure in fluids is spread equally throughout (forces act in all directions)
Hydraulic machines have the ability to use small forces to produce large forces, how would you calculate the force produced at one end if you are given the force at the other end and both areas?
P = F/A
F = f * A/a
i.e. if; f = 1N , a = 1cm2 , and , A = 50cm2 , then:
F = 50/1 * 1
F = [50N]
The system multiplies the force at “a” by a factor of 50x
How are the particles in a solid arranged?
Particles in solids are arranged in regular rows in planes. They are in an equilibrium where they oscillate about a fixed point but always return to their original position. This allows the solid to have a definite shape and volume while individual molecules still vibrate back and forth
How are particles in a liquid arranged? (5)
- The molecules in a liquid are farther apart than in a solid but still close enough to have a definite volume.
- They still vibrate but they also
- have the ability to slip past and flow over one another,
- never being close enough to bond and
- permanently take on the shape of their container
How are particles in a gas arranged?
- The particles in a gas are roughly ten times farther apart than in a solid or a liquid
- it is because of this that gases are much less dense and are easily compressible.
- The molecules move randomly and extremely high speeds, about 500m/s for air molecules at 0ºC, in all the available space
By what process solids become liquid?
(Melting)
By what process do liquids become solid?
(Freezing)
By what process do liquids become gas?
(Boiling)
Or
(Evaporation)
By what process do gases become liquid?
(Condensation)
By what process do solids become gas?
(Sublimation)
By what process do gases become solid?
(Deposition)
What does heating a gas inside a container cause? And why?
An (increase) in (pressure), this is due to the (thermal energy) causing the gas to move (faster) and (more regularly), meaning the (particles) hit the (inside) of the (container more often) thereby (increasing) the molecular force over the same area
What is a convection current? How are they caused?
They are (air currents) caused by changing (density) of (air). They occur when air (near to) a (heat source) is (heated up), (decreasing its density) causing it to (rise) replacing it with (cooler air) which is in turn (heated up), causing it to (rise) and the (cool air) to (fall), and so on and so forth
What happens to solids when heat is applied? Why?
They (expand) due the (thermal energy) causing the (molecules) to (vibrate) (more frequently) and across a (wider equilibrium)
What is a moment of a force?
A (moment) is a (turning force)
What factors affect the moment of a force? How do these factors affect the moment?
The (moment of a force) is dependant on the (magnitude of the force) and the (distance) it is away from the (fulcrum/pivot). The moment can be (increased) if (either or both) of these factors is (increased)
What is a lever?
A (lever) is any device which can (turn about a pivot). In a (working lever) a (force) called the (effort) can (overcome) the (resistive forces) known as the (load)
How can the stability of an object be increased?
1) lowering its centre of gravity
2) increasing the area of it’s base
When is a body in stable equilibrium?
If the body, when slightly displaced, returns to its original position, it is in stable equilibrium
E.g. ball in bowl (standing the right way up)
When is a body in unstable equilibrium?
If the body moves further away from its original position when slightly displaced
E.g. ball on upside down bowl
When is a body in neutral equilibrium?
If the body stays in it’s new position when displaced
E.g. ball on flat plane
What does the principal of conservation state?
Energy cannot be created or destroyed but can be transferred/conserved
State the formula for energy efficiency
Useful energy/power output
—————————————— = efficiency
Total energy/power input
What is the definition of a renewable energy source?
An energy source which can be replenished within a human lifetime and/or through natural processes
What is the definition of a non-renewable energy source?
An energy source which cannot be replenished within a human lifetime
What is the unit for energy efficiency?
There is no unit:
Only displayed in percentage and decimal form
State the formula for work done
W=FS
(W= work, F=force, S=displacement/distance traveled in direction of the force)
State the formulae for kinetic and gravitational potential energy
Ek = 1/2 mv2. (Kinetic energy)
Eg= mgh. (GPE)
State the rearranged formulae for kinetic energy
Ek = 1/2 mv2.
V=√2Ek/M
M=2Ek/v2
Ek
1/2. M. V2
State the formula for power
Power = work done/time taken
P= W/t
Or
P=fs/ t
Etc
What is the relationship between displacement and velocity squared in the equation for kinetic energy?
S is directly proportional to V2
What is another way to write the equation for kinetic energy (involving displacement)
F x S = 1/2mv2
S = 1/2mv2 / F
What surface it the best absorber and Emitter of radiation?
Conversely
What surface is the worst absorber and emitter of radiation?
A Matt Black surface
A shiny, chrome surface
What materials are the best conductors of heat generally
And
What materials are the worst conductors of heat (3 examples)
Metals (mostly)
Wood, water, air and wax etc.
What is the name of a poor conductor of heat?
A thermal insulator
How does convection work? (4)
- a substance is heated, increasing kinetic energy
- it becomes less dense and rises
- it then cools (less kinetic energy) and condenses (more dense)
- it then falls
How can we demonstrate convection (in water)
Heating Potassium Promanganate, which rises as purple streaks and falls once cooled
How can we prevent energy losses in buildings? Name 3 ways.
- Wall insulation (foam filled etc)
- double or triple glazed windows
- layers of insulating material (e.g. fibreglass) in a roof space between rafters
- carpets
- preventing draughts at doors
Etc.
What is the formula for beta radiation. What is it made of?
-10B
It is made of an electron lost by an unstable atom, where a neutron changes to a proton and electron
What type of radiation would be used in a factory to monitor the thickness of aluminium? Why? (2)
- Gamma ray or beta source because gamma rays unaffected by aluminium
- Only one that penetrates aluminium
Why is half-life important when choosing a radioactive source in a factory for aluminium thickness? (2)
- you need a Long half-life – e.g. several years
- So its activity remains constant/Source not changed often
Describe how count rate is used to control the thickness of aluminium in a roller machine (3)
- As the count rate decreases
- pressure (force) is increased (or converse)
- To make metal thinner
What is the name of an isotope of hydrogen with a mass of 2?
Deuterium
What is the name of an isotope of hydrogen with a mass of 3?
Tritium
What is the formula for alpha radiation. What is it made of?
24He or 24a etc.
It is made of 2 protons and 2 neutrons, ejected by an unstable nucleus
It has the same properties as a helium atom
What is background radiation?
Radiation from our environment which we are constantly exposed to
From the sun (cosmic), hospitals, our bodies, rocks etc.
Outline how Rutherford conducted the alpha-particle experiment (6)
-
Vacuum – to prevent collision with air molecules
Alphas have limited range in air - Measurements – Move detector to different angles Measure the number of alphas detected
- Deflection – The positive particles repelled by nucleus The nucleus is positive or Like charges repel
- Small nucleus – Most alphas passed through without deflection
- Massive nucleus – Some alphas rebounded or were back scattered
What three isotopes are used in nuclear fusion?
Where can they be extracted from?
Hydrogen
Deuterium
Tritium
In the seas/oceans
What is the major product of nuclear fusion?
Helium
What is the formula for average velocity?
avgV = V-U/2
