Physics Paper 2 Flashcards
What is a vector quantity?
A quantity with magnitude and direction
Give 2 examples of vector quantities.
Displacement, velocity
What is a scalar quantity?
A quantity with magnitude only
Give 2 examples of scalar quantities.
Distance, speed
What is the typical speed for walking?
1.5m/s
What is the typical speed for running?
3m/s
What is the typical speed for cycling?
6m/s
What is the typical speed for a car?
13 - 30m/s
What formula relates speed, distance and time?
Speed = distance/time v = s/t
What is velocity?
Speed in a given direction; rate of change of displacement
What is acceleration?
Rate of change of velocity
What is represented by the enclosed area in a velocity-time graph?
Distance travelled
What formula links velocity, time and acceleration?
Acceleration = change in velocity/time taken
a = v/t
(HT) What are the characteristics of speed and velocity in a circular orbit?
Constant speed, changing velocity
State Newton’s first law of motion
If there is no resultant force on an object, it ill continue with a constant velocity if moving or remain at rest if stationary
What does Newton’s first law tell us about objects moving with uniform velocity?
The resultant force on the object must be zero
What does Newton’s first law tell us about objects moving with changing speed or direction?
There must be a resultant force on the object
State Newton’s second law of motion
Force = mass x acceleration
F = ma
(HT) What is inertial mass?
A measure of how difficult it is to change the velocity of an object: the ratio of force over acceleration
State Newton’s third law of motion
Every force is paired with an equal and opposite reaction force
(HT) What is momentum?
The quantity of motion of a moving object: the product of mass and velocity
(HT) What is the formula for momentum?
Momentum = mass x velocity
p = mv
(HT) What happens to momentum in collisions?
It is conserved: total momentum before the collision = total momentum after the collision
What dangers are caused by large decelerations in events such as car crashes?
Large forces on passenger can lead to serious injury
What is a typical human reaction time?
0.25s
Describe 2 ways of measuring reaction time
Dropping a ruler and catching it, computerised tests involving pressing a button in response to seeing something on the screen - time recorded by the computer
What is stopping distance?
The total distance travelled by a car during the time between the driver seeing the hazard and the car coming to rest
What is thinking distance?
The distance travelled by the car while the driver reacts to the hazard
What is braking distance?
The distance travelled by the car while the brakes do work on the wheels to bring them to a stop
What factors affect thinking distance?
Speed, alcohol, drugs, tiredness, distractions
What factors affect stopping distance?
Speed, condition of the road, weather conditions, condition of tyres, condition of brakes
What are the units of velocity?
m/s
metres per second
What are the units of acceleration?
m/s2
metres per second per second
What are the units of force?
N (newtons)
What are the units of displacement?
m (metres)
(HT) What are the units of momentum?
kg m/s (kilogram-metres per second)
Name 3 non-contact forces
Gravity, electrostatic, magnetism
Name 2 contact forces
Friction, the normal contact force
What is weight?
The force on an object due to its mass in a gravitational field
What is the unit of weight?
N (newtons)
What formula relates weight, mass and gravitational field strength?
W = mg
Weight = mass x gravitational field strength
What conditions must occur in order for an object to be bent, compressed or stretched?
More than one force must be applied
What is the difference between elastic and inelastic deformation?
Elastic deformation: the object will return to its original size and shape.
Inelastic deformation: the object will not return to its original size and shape.
What is “work done”?
The energy transferred when a force is used to move an object across a distance
What formula relates work done, force, and distance?
W = fd
Work done = force × distance
What is 1 newton-metre equivalent to?
1 joule
What is a typical speed for a train?
56m/s
What is a typical speed for a plane?
250m/s
What is the amplitude of a wave?
The maximum displacement of a point on a wave from its undisturbed position
What is the wavelength of a wave?
The distance across one complete wave cycle
What is the time period of a wave?
The time for one complete wave cycle to pass a point
What is the frequency of a wave?
The number of wave cycles to pass a point per second
What formula links wave velocity, frequency, and wavelength?
v = fλ
velocity = frequency × wavelength
What are the features of transverse waves?
The wave travels at right angles to the direction of oscillations
What are the features of longitudinal waves?
The wave travels parallel to the direction of oscillations
Give an example of transverse waves
Ripples on water
Give an example of longitudinal waves
Sound waves
Describe evidence for the fact that ripples on water transfer energy but not matter
An object floating on water will bob up and down but will not move across when a wave travels across the water
Describe evidence for the fact that sound waves in air transfer energy but not matter
A helium balloon will move side-to-side but will not travel across when a sound wave travels through the air
What is the unit for wavelength?
m (metres)
Name the 7 groups in the electromagnetic spectrum
Radio, microwaves, infra-red, visible, ultraviolet, X-rays, gamma rays
Which part of the electromagnetic spectrum can our eyes detect?
Visible (light)
Which part of the electromagnetic spectrum has the longest wavelength/lowest frequency?
Radio
Which part of the electromagnetic spectrum has the shortest wavelength/ highest frequency?
Gamma
(HT) What 4 things can happen when a wave interacts with matter?
Absorption, transmission, reflection, refraction
(HT) What 2 things does the interaction of a wave with matter depend on?
The material and the frequency of the wave
(HT) What causes refraction?
Changes to a wave’s velocity in different media
(HT) What happens to wave fronts when a wave travels from a less dense to a more dense medium?
They get closer together
(HT) How can radio waves be produced by a circuit?
Alternating p.d. causes electrons in the circuit to oscillate, emitting radio waves
(HT) What happens when radio waves are absorbed by a wire in a circuit?
Electrons in the circuit absorb the waves and oscillate, producing an alternating current
Describe two ways that atoms can produce electromagnetic waves
Changes in the nucleus (oscillating proton) or changes to electrons (changing distance from nucleus)
Changes in the nucleus (oscillating proton) or changes to electrons (changing distance from nucleus)
Electrons can be moved to different distances from the nucleus or they can be knocked out and the atom becomes ionised
State a use of radio waves
Television and radio communication
State 2 uses of microwaves
Satellite communication (inc. mobile phones), cooking
State three uses of infra-red waves
Night-vision cameras, remote controls, cooking
State a use of visible light
Fibre-optics
State 3 uses of ultra-violet light
Fluorescent light bulbs, tanning beds, counterfeit note detection
State 2 uses of X-rays
X-ray photography for medical diagnosis, security scans for airport luggage
State 2 uses of gamma waves
Radiotherapy, sterilising medical equipment
What factors affect the frequency of an electromagnetic wave?
The type of charged particle oscillating; the frequency of the oscillation
Give 2 examples of electromagnetic waves transferring energy from emitter to absorber
Energy is transferred from the Sun (emitter) via visible light to the Earth (absorber); energy is transferred from an X-ray machine (emitter) via X-rays to bones and photographic plate (absorbers)
What are the hazards from UV waves?
Ageing of the skin, ionisation in cells can lead to skin cancer
What are the hazards from X-rays and gamma rays?
Ionisation in cells can lead to cancer
What 3 things do all electromagnetic waves have in common?
They are all transverse waves, they all travel at the same speed in a vacuum, they all transfer energy from emitter to absorber
Describe the force between like poles
Repels
Describe the force between unlike poles
Attracts
What is a permanent magnet?
A magnet that creates its own magnetic field
What is an induced magnet?
An object that has a magnetic field due to being in the magnetic field of another magnet
What direction does a magnetic field always act in?
From north to south
Where is a magnetic field the strongest?
Next to the poles of the magnet
What happens to the strength of a magnetic field as you move further from the magnet?
It decreases
How do magnetic compasses provide evidence that the Earth’s core must be magnetic?
The compass needle always points
North, indicating that it is aligning itself with a magnetic field from the Earth
What is the magnetic field like around a current-carrying wire?
Circular around the wire
What factors affect the strength of a magnetic field due to a current-carrying wire?
Strength of the current, distance from the wire
How does a solenoid enhance the magnetic field due to a current-carrying wire?
When a current-carrying wire is wrapped around an iron core, the iron becomes an induced magnet and its field combines with that of the wire.
How does an electric motor work?
The force on a current-carrying wire in a magnetic field pushes one side of a coil down and the other side up.
