physics o levels

what are the scalar quantities

energy, length, mass time

what are the vector quantities

displacement, velocity, acceleration, force

what is the frequency of a ticker tape

50Hz

what does the period of the pendulum depend on

the length and the gravitational field strength (the longer the length, the longer the period, the larger the grams and the shorter the period)

what is displacement

the distance travelled in a specific direction

what is speed

the rate of change of distance

what is velocity

the rate of change of displacement

what does uniform acceleration mean

the rate of change of velocity is constant

what does the size of terminal velocity reach depend on

the weight of the object heavier objects will have a higher terminal velocity

how does acceleration change in the presence of air resistance when an object is falling

as the object accelerates, its speed increases, hence the air resistance increase. acceleration decreases. the resultant force is weight - air resistance

what happens in terms of forces when an object is falling without air resistance

only the weight acts on the object, cuaisng it to acceleration at approximately 10m/s2

what is the resultant force when terminal velocity is reached

0 because the weight equals to the air resistance

does tension act towards or away from an object

tension always acts away from the object

what is newton’s first law of motion

an object at rest will remain at rest and an object in motion will continue at constant speed in a straight line in the absence of a resultant force acting on It

what is newton’s second law of motion

the resultant force acting upon an object is equal to the product and the mass and the acceleration of the object, the direction of the force is the same as that of the object’s acceleration

what happens if the resultant force is in the direction of motion

the object will accelerate

what happens if the resultant force is opposing the motion

the object will decelerate till it comes to a stop

what is newton’s third law of motion

for every action (force), there is an equal and opposite reaction, and these forces act on mutually opposite bodies

define mass

the amount of matter in a body

what is inertia

reluctance of a body to change its state of rest or motion, due to its mass

what is earth’s gravitational field

a region around the earth where a mass will experience a force of attraction due to the earth

define gravitional field strength

the gradational force acting on unit mass of a body

what are the characteristics of mass

it is the amount of substance in the body, it si constant in any location, it is a scalar quantity, it is measured in kilograms, and It is measured using a beam balance

what are the characteristics of weight?

it is the graviotnal force acting on the body, it depends on the acceleration due to gravity at the location, it is a vector quantity, measured in newtons and it is measured using a spring balance

define density

the mass per unit volume of an object

deinfe the moment of a force

the product of the force and the perpendicular distance from the pivot to the line of action of the force

if the perpendicular distance from the pivot is larger, is the force required reduced or increased to have the same moment

reduced

define the principle of moments

when an object is in equilibrium the sum of clockwise moments taken about a point is equal to the sum of anticlockwise moments taken about the same point

define the centre of gravity

the point through which the entire weight of the object appears to ct for any orientation of the object

define pressure

the force acting per unit area

how is nuclear energy released

the splitting of heavy nuclei of the fusion of light nuclei

define the prinipal of conservation of energy

energy cannot be created or destroyed, but it can be changed from one form into another. Total amount of energy in an isolated system remains constant

define work done

the product of the force on a body and the distance moved by the body in the direction of the force

define acceleration

the rate of change of velocity

define power

the rate of work done or rate of energy transfer

what is the formula for power is the object moves at constant speed

force x velocity

define efficiency

the energy converted to useful output/ total energy input x 100%

define instantaneous speed

the speed at a particular moment

what does the kinetic model of matter state

all matter is made up of tiny particles such as atoms or molecules which are in constant random motion

what is Brownian motion

the observed random or irregular motion of smoke particles in air

what does Brownian motion illustrate

it illustrates the kinetic model of matter that air molecules are in contours random motion

why do the smoke particles move randomly

the smoke particles are hit by fast moving air molecules

what causes a change in volume occupied by a fixed mass of gas at constant pressure?

the temperature of the gas. As the temerpature of the gas increases, ht kinetic energy of the molecules increases, and the speed of the molecules increases. this will allow the molecules to hit the walls with a greater force and move frequently , increasing the pressure within the container and the differentce in pressure results in a force that pushes the container outwards and the volume increases until the pressure on the inside and the pressure eon the outside is equalised

what is the internal energy of an object related to

the temperature, the higher the temperature of the object, the more internal energy it has

when is thermal equilbrium reached

when there is no net transfer of energy. two different objects in contact reach the same temperature

describe conduction for objects that are not metals

When one and of an object is heated, the molecules gain energy and vibrate faster. These molecules collide with their neighbouring molecules and thermal energy is transferred to them. These molecules in turn vibrate faster and transfer the thermal energy to itsneighbouring molecules. This transfer of energy from molecule to molecule will continue. until the other end of the object reaches the same temperature as the heated end.

describe conduction for metal

when an object is heated, the free elections gain energy and move faster, these electrons are able to travel in the spaces between molecules and transfer energy to other free electrons

define conduction

the process whereby energy is transferred by the vibrations of atoms or molecules without any flow of the material medium

define convection

the process whereby energy is transferred by means of currents in a fluid (liquid or gas) because of a difference in density

why can convection not occur in solids

it involves the bulk movement of a fluid, since the solid particles are fixed in positions, the particles in the solid cannot transfer the energy by moving about freely

describe convection in fluids (liquids and gases)

When a liquid is heated, it expands and becomes less dense. The heated liquid then rises and the colder liquid being denser will move down to replace it. The movement of the liquid is known as convention current.

define radiation

the transfer of thermal energy in the form of electromagnetic waves such as infrared radiation without the aid of a medium

define heat capacity

energy needed to raise the temperature of a substance by 1 kelvin.

define specific heat capacity

amount of energy needed per unit mass to raise a temperature of a substance by one kelvin

specific heat capacity formula

energy / mass x change in temperature

define latent heat

the amount of thermal energy absorbed or released during a change of state without a change in temperature

define specific latent heat of fusion

the amount of thermal energy per unit mass required to change a substance from solid to liquid without a change in temperature

define specific latent heat of vaporisation

the amount of thermal energy required per unit mass to change a substance from liquid to gas, without a change in temperature

define the speed of the wave

the distance moved by the wave per unit time.

define the frequency of a wave

the number of complete waves produced per second.

define wavelength

shortest distance between any two points in the waves that are in phase.

define period

time taken for 1 pt on the wave to complete one oscillation.

define amplitude

the maximum displacement from the rest position

define wave front

an imaginary line on a wave that joins all points that are in the same phase

define longitudinal waves

waves that travel in a direction parallel to the direction of vibration egsound wave.

define transverse waves

waves that travel in a direction perpendicular to the direction of vibrations for example water waves and all EM waves

what happens to water waves when they travel from deep to shallow water

speed decreases, so the wavelength decreases

what happens when light waves passes from a less dense to desner medium

the speed will decrease, since frequency remains constant, the wavelength will decrease

why can sound not be transmitted through vaccum

this is because there are no particles to vibrate to transmit sound

between what range and what range can humans hear

20Hz and 20 000Hz

How is ultrasound used in prenatal scanning

they are sent into the body using a transmitter, the echoes that are produced by the reflection at the boundaries of different tissues are converted into a picture called a sonogram and the foetus can then be examined

define refraction

the bending of a light ray as it travels across the boundary separating two optical media

what is the first law of refraction and reflection

the incident ray, the refracted ray and the normal all lie on the same plane

wat is the second law of refraction

for 2 given media, the ratio of the sine of the angle of incidence to the sine of the angle of refraction is a constant

what is the second law of reflection

the angle of incidence is equal to the angle of reflection

when does total internal reflection occur

when light passes from an optically denser to a less dense medium, and the angle of incidence in the optically denser medium is greater than the critical angle

what happens when TIR occurs

When light travels from a denser medium to a less dense medium, when the angle of incidence is greater than the critical angle, the ray will not be refracted but instead will be reflected back into the denser medium.

what is the focal length

the distance from the optical centre to the focal point

what is the focal point

the point at which all rays parallel to the principal axis converge to after refraction by a lens

what is the speed of EM waves in a vacuum

3.0 × 10^8

applications for radio waves

broadcasting and communications eg FM radio, military satellite communications

what are microwaves used for

cooking food as microwaves are absorbed by water molecules causing them to vibrate and heat up, satellite transmissions

what is infrared radiation used for

heater and night vision equipment, television remote controls

what are ultraviolet rays used for

fluorescent lamps, sterilise workspaces and tools used in biology laboratories

what are x rays used for

to produce x ray images for medical diagnosis, and to detect structural probelms and cracks in metals that cannot be seen from the outside

what are gamma rays used for

kill cancer cell in medical treatments

whu are ionising radiations harmful

they have high energy to break chemical bonds producing ions that are reactive, they damage DNA in cells which can lead to cancer

what radiation are ionising

ultra violet, x rays, gamma rays

what radiation are non ionising

radio waves, microwaves, infasred, visible light

define electric field

region in which an electric charge experiences an electric force

what direction is the direction of the electric field on negative charges

towards the negative charge I is the opposite for positive charge

define current

rate of flow of electric charge

define conventional current

the movement of positive charges from the positive end to the negatve end of an electric source

define electromotive force

the total work done by a source (battery) in driving a unit charge

round a complete circuit.

define potential difference

the work done to drive a unit charge

through the component (between 2 pts).

when does the resistance of a thermistor and LDR increase

when the temperature increases and the light intensity increases

define resistance

the ratio of potential difference across a component to teh current flowing through it

define ohm’s law

the current flowing through a conductor is directly proportional to the potential difference applied across it, given the physical conditions are kept constant

What are some hazards of using electricity

1. damaged insulation van case electric shock to the suer if he touches the bare wires

2. the overheating of cables can result in electric fires

3. damp conditions can cause electric shock and electrocution

what is a fuse

a safety device included in an electrical circuit to prevent an excessive flow of current