Paper 2

Question 1

name two examples of a scalar quantity and two examples of a vector quantity

Answer 1

scalar: speed/distance/mass/temperature
vector: displacement/momentum/force/acceleration/
velocity

Question 2

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

Answer 2

contact force: air resistance
non contact force: gravitational force

Question 3

explain the difference between scalar and vector quantities and contact and non contact forces

Answer 3

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

Question 4

what is the formula for calculating the weight of an object

Answer 4

weight (N) = mass (kg) x gravitational field strength (N/kg)

Question 5

what is a free body diagram

Answer 5

a model of the forces acting on an object

Question 6

give the formula for calculating work done by a force

Answer 6

work done(j) = force(n) x distance(moved along the line of action of the force) (m)

Question 7

how many joules of work done does 1 Nm equal

Answer 7

one joule

Question 8

describe the forces acting on an object in equilibrium

Answer 8

if all of the forces acting on an object combine to give a resultant force of zero, the object is in equilibrium

Question 9

what is the difference between an elastic and an inelastic deformation

Answer 9

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

Question 10

equation for force extension and spring constant of an object

Answer 10

force (N) = Spring constant (N/m) x Extension (m)

Question 11

what is the limit of proportionality

Answer 11

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.)

Question 12

how do you find the following from a linear force extension graph
a) spring constant
b)work done

Answer 12

a) the gradient of the straight line is equal to the spring constant
b) force x distance on the graph

Question 13

define a moment and state an equation for calculating the size of a moment

Answer 13

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)

Question 14

if a seesaw is balanced what can you say about the moments?

Answer 14

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)

Question 15

explain why the pressure increases as you go deeper into a column of a liquid

explain why density of liquid effects pressure

Answer 15

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

Question 16

what causes an object to float or sink

Answer 16

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

Question 17

explain how and why atmospheric pressure varies with height

Answer 17

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

Question 18

what is the difference between displacement and distance

Answer 18

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

Question 19

define acceleration in terms of velocity and time

Answer 19

acceleration = change in velocity (m/s) divided by time (s)

Question 20

what does uniform acceleration mean

Answer 20

speeding up or slowing down at a constant rate

Question 21

what does the gradient represent for a distance time graph

Answer 21

gradient= speed (steeper the graph the faster its going

Question 22

what does the gradient represent for a velocity time graph

Answer 22

gradient = acceleration

Question 23

what is terminal velocity and what causes it

Answer 23

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.)

Question 24

state newtons three laws of motion

Answer 24

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

Question 25

what is inertia

Answer 25

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

Question 26

what is the stopping distance of a vehicle?

Answer 26

the thinking distance combined with the braking distance

Question 27

state 4 things that can affect the braking distance of a vehicle

Answer 27

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

Question 28

give two things that affect a persons reaction time

Answer 28

tiredness/drugs/alcohol/distraction

Question 29

what is an average reaction time

Answer 29

typical human reaction time is between 0.2 and 0.9s

Question 30

explain momentum before=momentum after

Answer 30

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

Question 31

state the formula used to calculate an objects momentum

Answer 31

momentum (kg m/s) = mass (kg) x velocity (m/s)

Question 32

explain how car safety features use momentum and forces to reduce the risk of injury to passengers

Answer 32

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

Question 33

explain how crashmats and bike helmets use momentum and forces to reduce the risk of injury to passengers

Answer 33

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

Question 34

what affects thinking distance

Answer 34

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

Question 35

what is thinking distance

Answer 35

how far the car travels during the drivers reaction time

Question 36

what is braking distance

Answer 36

the distance taken to stop under the braking force

Question 37

what is the amplitude of a wave

Answer 37

the amplitude of a wave is the maximum displacement of a point on the wave from its undisturbed position

Question 38

what is the frequency of a wave

Answer 38

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)

Question 39

what is the period of a wave

Answer 39

the amount of time it takes for a full cycle of the wave

Question 40

describe the difference between transverse and longitudinal waves and give and example of each kind

Answer 40

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

Question 41

state the law of reflection

Answer 41

angle of incidence = angle of reflection

Question 42

define specular and diffuse radiation

Answer 42

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

Question 43

true or false? all electromagnetic waves are transverse

Answer 43

true all em waves are transverse waves that transfer energy from a source to an absorber

Question 44

explain refraction

Answer 44

when a wave crosses a boundary between materials at an angle and it changes direction- its refracted

Question 45

what kind of current is used to generate radio waves in an antenna

Answer 45

alternating current

Question 46

explain why microwaves are used for satellite communication and mobile phone signals

Answer 46

they can pass easily through earths watery atmosphere

Question 47

give an every day use of infrared radiation

Answer 47

infrared cameras and electric heaters

Question 48

what type of radiation is used to transmit a signal in an optical fibre

Answer 48

infrared- light rays

Question 49

name the type of radiation produced by the lamps in tanning salons

Answer 49

ultraviolet

Question 50

what does the term ionising radiation mean

Answer 50

Ionising radiation refers to radiation that has enough energy to break an electron away from an atom, a process called ionisation.

Question 51

what does radiation dose in sieverts measure

Answer 51

radiation dose measured in sieverts is a measure of the risk of harm from the body being exposed to radiation

Question 52

give the three rules for refraction in a convex lens and the three for a concave lens

Question 53

explain the terms real image and virtual image

Answer 53

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

Question 54

true or false opaque objects transmit light

Answer 54

false opaque objects dont transmit light, when visible light waves hit them they absorb some wavelengths of light and reflect others

Question 55

describe how colour filters work

Answer 55

colour filters filter out different wavelengths of light, so that only certain colours are transmitted, the rest are absorbed

Question 56

describe the rates of radiation absorbtion and emission for an object at a constant temperature

Answer 56

objects at a constant temperature emit infrared radiation at the same rate that they are absorbing it

Question 57

what is a perfect black body

Answer 57

an object that absorbs all of the radiation that hits it, no radiation is reflected or transmitted

Question 58

what is a leslie cube?

Answer 58

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.

Question 59

explain how absorbtion relection and emission of radiation affects the earths temperature

Answer 59

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.

Question 60

what is the frequency range of human hearing

Answer 60

20- 20,000 Hz

Question 61

explain how ultrasound is used in prenatal scanning industry and echo sounding

Answer 61

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

Question 62

how can s and p waves be used to explore the structure of earths core

Answer 62

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.

Question 63

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

Answer 63

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.