Paper 2 Flashcards
name two examples of a scalar quantity and two examples of a vector quantity
scalar: speed/distance/mass/temperature
vector: displacement/momentum/force/acceleration/
velocity
a tennis ball is dropped from a height. name one contact force and one non contact force that act on the ball as it falls
contact force: air resistance
non contact force: gravitational force
explain the difference between scalar and vector quantities and contact and non contact forces
vector quantities have a magnitude and direction- scalar quantities have magnitude but no direction
contact force: when two objects have to be touching for a force to act
non contact force: if objects do not need to be touching for the force to act
what is the formula for calculating the weight of an object
weight (N) = mass (kg) x gravitational field strength (N/kg)
what is a free body diagram
a model of the forces acting on an object
give the formula for calculating work done by a force
work done(j) = force(n) x distance(moved along the line of action of the force) (m)
how many joules of work done does 1 Nm equal
one joule
describe the forces acting on an object in equilibrium
if all of the forces acting on an object combine to give a resultant force of zero, the object is in equilibrium
what is the difference between an elastic and an inelastic deformation
an object has been elastically deformed if it can go back to its original shape and length after force has been removed
an object has been inelastically deformed if it doesnt return to its original shape and length after the force has been removed
equation for force extension and spring constant of an object
force (N) = Spring constant (N/m) x Extension (m)
what is the limit of proportionality
Limit of proportionality is the point which if exceeded, the spring extension will no longer be proportional to the load. (Usually, when we pull a spring, it will restore back to the original length once the pulling force is removed. If pulled hard enough, the spring will not spring back to the original length.)
how do you find the following from a linear force extension graph
a) spring constant
b)work done
a) the gradient of the straight line is equal to the spring constant
b) force x distance on the graph
define a moment and state an equation for calculating the size of a moment
a force can cause an object to rotate- the turning effect of a force is called its moment
moment of a force (Nm) = Force (N) x Distance (m)
if a seesaw is balanced what can you say about the moments?
when a seesaw is balanced its moments are equal (the moment of each person on the seesaw equals their weight x their distance from the pivot)
explain why the pressure increases as you go deeper into a column of a liquid
explain why density of liquid effects pressure
the more dense a given liquid is the more particles it has in a certain space. this means theres more particles that are able to collide so the pressure is higher
as the depth of the liquid increases the number of particles above that point increases. The weight of these particles adds to the pressure felt at that point so liquid pressure increases with depth
what causes an object to float or sink
if the upthrust on an object is equal to the objects weight then the forces balance and the object floats, if its weight is more then the upthrust the object sinks
explain how and why atmospheric pressure varies with height
how:
there are fewer air molecules above a surface as the height increases. this means that the weight of the air above it which contributes to the atmospheric pressure, decreases with altitude
why:
atmospheric pressure is created on a surface by air molecules colliding with the surface- as altitude increases atmosphere gets less dense so theres fewer air molecules that are able to collide with the surface
what is the difference between displacement and distance
distance is scalar, displacement is vector
distance is how far an object has moved, its a scalar quantity because it doesn’t include direction
displacement is a vector quantity because it measures the distance and direction in a straight line from an objects starting point to its finishing point
eg if you walk 5m north then 5m south your displacement is 0m but the distance travelled is 10 m
define acceleration in terms of velocity and time
acceleration = change in velocity (m/s) divided by time (s)
what does uniform acceleration mean
speeding up or slowing down at a constant rate
what does the gradient represent for a distance time graph
gradient= speed (steeper the graph the faster its going
what does the gradient represent for a velocity time graph
gradient = acceleration
what is terminal velocity and what causes it
Terminal velocity is a steady speed achieved by an object freely falling through a gas or liquid (maximum velocity attainable by an object as it falls through a fluid. It occurs when the sum of the drag force and the buoyancy is equal to the downward force of gravity acting on the object. Since the net force on the object is zero, the object has zero acceleration.)
state newtons three laws of motion
In the first law, an object will remain at rest, and an object in motion will remain in motion unless it is acted upon by an external force
In the second law, the force acting on an object is equal to its mass times its acceleration. F=m(kg) x a (m/s2)
In the third law, when two objects interact, they apply forces to each other of equal magnitude and opposite direction. for every action there is an equal and opposite reaction
what is inertia
until acted upon by a resultant force objects at rest stay at rest and objects moving at a steady speed will stay moving at that speed (newtons first law) this tendency to continue in the same state of motion is called inertia
what is the stopping distance of a vehicle?
the thinking distance combined with the braking distance
state 4 things that can affect the braking distance of a vehicle
SPEED- faster a vehicle travels the longer it takes to stop
WEATHER/ROAD SURFACE- wet or icy or leaves or oil- less grip so less friction between a vehicles tyres and the road which cab cause tyres to skid
CONDITION OF TYRES- if the tyres on a vehicle have no tread left they cant get rid of water in wet conditions this leads to them skidding on top of the water
BRAKES- if brakes are worn or faulty they wont be able to supply as much force as well maintained brakes
give two things that affect a persons reaction time
tiredness/drugs/alcohol/distraction
what is an average reaction time
typical human reaction time is between 0.2 and 0.9s
explain momentum before=momentum after
in a closed system, the total momentum before an event (e.g. collision) is the same as after the event. This is called conservation of momentum
state the formula used to calculate an objects momentum
momentum (kg m/s) = mass (kg) x velocity (m/s)
explain how car safety features use momentum and forces to reduce the risk of injury to passengers
crumple zones: crumple on impact, increasing the time taken for the car to stop
seat belts: stretch slightly, increasing the time taken for the wearer to stop
air bags: inflate before you hit the dashboard of a car the compressing air inside it slows you down more gradually than if you had just hit the hard dashboard
explain how crashmats and bike helmets use momentum and forces to reduce the risk of injury to passengers
bike helmets contain a crushable layer of foam which helps to lengthen the time taken for your head to stop in a crash. This reduces the impact on your brain
crash mats and cushioned flooring increase the time taken for you to stop if you fall on them, this is because they are made from soft compressible materials
what affects thinking distance
SPEED- The faster your going the further you’ll travel during the time you take to react
REACTION TIME- the longer your reaction time the longer your thinking distance
what is thinking distance
how far the car travels during the drivers reaction time
what is braking distance
the distance taken to stop under the braking force
what is the amplitude of a wave
the amplitude of a wave is the maximum displacement of a point on the wave from its undisturbed position
what is the frequency of a wave
the frequency of a wave is the number of complete waves passing a certain point per second ( measured in hertz, 1hz is 1 wave per second)
what is the period of a wave
the amount of time it takes for a full cycle of the wave
describe the difference between transverse and longitudinal waves and give and example of each kind
in transverse waves the ocillations are perpendicular (90 degrees) to the direction of energy transfer, most waves are transverse including: all electromagnetic waves, ripples and waves in water, a wave on a string
in longitudinal waves the oscillations are parallel to the direction of energy transfer
examples are: sound waves in air: ultrasound
shock waves eg seismic waves
state the law of reflection
angle of incidence = angle of reflection
define specular and diffuse radiation
specular: when a wave is reflected in a single direction by a smooth surface e.g. when light is reflected by a mirror you get a nice clear reflection
diffuse: when a wave is reflected by a rough surface like a piece of paper and the reflected rays are scattered in different directions
true or false? all electromagnetic waves are transverse
true
all em waves are transverse waves that transfer energy from a source to an absorber
explain refraction
when a wave crosses a boundary between materials at an angle and it changes direction- its refracted
what kind of current is used to generate radio waves in an antenna
alternating current
explain why microwaves are used for satellite communication and mobile phone signals
they can pass easily through earths watery atmosphere
give an every day use of infrared radiation
infrared cameras and electric heaters
what type of radiation is used to transmit a signal in an optical fibre
infrared- light rays
name the type of radiation produced by the lamps in tanning salons
ultraviolet
what does the term ionising radiation mean
Ionising radiation refers to radiation that has enough energy to break an electron away from an atom, a process called ionisation.
what does radiation dose in sieverts measure
radiation dose measured in sieverts is a measure of the risk of harm from the body being exposed to radiation
give the three rules for refraction in a convex lens and the three for a concave lens
explain the terms real image and virtual image
a real image is where the light from an object comes together to form an image on a screen, like the image formed on an eyes retina
a virtual image is when the rays are diverging so the light from the object appears to be coming from a completely different place
true or false opaque objects transmit light
false
opaque objects dont transmit light, when visible light waves hit them they absorb some wavelengths of light and reflect others
describe how colour filters work
colour filters filter out different wavelengths of light, so that only certain colours are transmitted, the rest are absorbed
describe the rates of radiation absorbtion and emission for an object at a constant temperature
objects at a constant temperature emit infrared radiation at the same rate that they are absorbing it
what is a perfect black body
an object that absorbs all of the radiation that hits it, no radiation is reflected or transmitted
what is a leslie cube?
Leslie’s cube is a device used in the measurement or demonstration of the variations in thermal radiation emitted from different surfaces at the same temperature.
explain how absorbtion relection and emission of radiation affects the earths temperature
the overall temperature of the earth depends on the amount of radiation it reflects absorbs and emits
during the day lots of radiation is tranferred from the sun and absorbed. this causes an increase in local temperature.
what is the frequency range of human hearing
20- 20,000 Hz
explain how ultrasound is used in prenatal scanning industry and echo sounding
ultrasound waves can pass through the body but whenever they reach a boundary between two different media (like fluid in the womb and the skin of the foetus) some of the wave is reflected back and detected
it can be used to find flaws in objects such as pipes or materials such as wood or metal, when entering a material they will usually be reflected by the far side of the material, if theres a crack inside the object the wave will be reflected sooner
how can s and p waves be used to explore the structure of earths core
P waves are detected on the opposite side of the Earth. Refractions between layers cause two shadow zones, where no P waves are detected – the size and positions of these shadow zones indicate there is a solid inner core.
S waves are not detected on the opposite side of the Earth – this suggests that the mantle has solid properties, but the
outer core
must be liquid.
This graph shows the velocity of a falling object against time. Explain how changing forces on the object cause the graph to reach a maximum.
v|
e|—————————-
l | ~~~~~~~~~~~
o| /
c|/
i|—————————->
t time
y
As velocity increases, the drag force experienced by the object increases as well. As the force of gravity acting on the object doesn’t change, the resultant force acting on the object decreases as its velocity increases. This means that the acceleration of the object also decreases. The acceleration keeps decreasing until it reaches zero, at which point the velocity of the object becomes constant — it stops increasing and reaches a maximum.
