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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
damaged insulation van case electric shock to the suer if he touches the bare wires
the overheating of cables can result in electric fires
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
