3-6 Markers

Question 1

Explain the factors that affect the distance needed to stop a car in an emergency? 3

Answer 1

• reaction time explained in terms of longer reaction times increase thinking distance
• taking drugs / drinking alcohol / tiredness / age /distractions
• explained in terms of effect on driver’s reaction time & speed
• the faster the vehicle the greater the distance travelled in the driver’s reaction time
• explained in terms of increased speed increases Ek so increases work done to stop the car
• condition of the tvres /condition of road surface /wet/ic roads
• explained in terms of condition of tres and road surface (weather) affecting friction
• condition of brakes explained in terms of effect on braking force or reduced friction
• mass / weight of vehicle

Question 2

Since 1965, all cars manufactured for use in the UK must have seat belts.
Explain why It is safer for a car driver to be wearing a seat belt, compared with not wearing a seat belt, if the car is involved in a collision (3)

Answer 2

• the seat belt stretches
• driver takes a longer (impact) time to slow down and stop (than a driver hitting part of the car
• for the (same) change of momentum
• a smaller force is exerted (so driver less likely to have serious injury than driver without seat belt)

Question 3

When hitting the golf ball, the golfer swings the golf club to keep it in contact with the golf ball for as long as possible. The force acting on the golf ball is constant during this time.
Explain the effect that the time of contact between the golf club and the golf ball has on the distance the golf ball travels.

Answer 3

• The longer the time of contact the greater the change of momentum
• since the mass of the golf ball is constant
• the velocitv of the golf ball must increase
• increasing the distance the golf ball travels

Question 4

Explain why the pressure in a gas increases as the gas is compressed (4)

Answer 4

• (as the gas is compressed) the volume of gas decreases
(S) Gas Pressure
• so more frequent collisions of gas particles with container walls
• each particle collision with the wall causes a force
• (so there is a) greater force on walls

Question 5

Explain why atmospheric pressure decreases with increasing altitude (3)

Answer 5

• air molecules colliding with a surface create pressure
• at increasing altitude distance between molecules increases
• at increasing altitude fewer molecules
• so number of collisions with a surface decreases
• or so always less weight of air than below

Question 6

A swimmer dives below the surface of the sea, explain how the pressure on the swimmer changes as they swim to a greater depth (2)

Answer 6

• increasing depth increases the volume water above
• increasing the weight (of water) acting on the swimmer

Question 7

Describe how you can use the image on a screen beneath a ripple tank to measure the wavelength, frequency and speed of a water wave (4)

Answer 7

• measure the length of a number of waves on screen
• divide the length by the number of waves to give wavelength
• count the number of waves passing a point in a given time
• divide the number of waves counted by the time for frequency
• multiply frequency and wavelength to calculate wave speed

Question 8

Describe the difference between transverse waves and longitudinal waves (3)

Answer 8

• Longitudinal waves, the oscillations / vibrations are parallel to the direction of energy transfer
• Transverse waves, the oscillations / vibrations are at 90 degrees (perpendicular) to the direction of energy transfer

Question 9

Compare the wavelengths & frequencies of radio waves and gamma waves (3)

Answer 9

Gamma waves: highest frequencies and shortest wavelength
Radio waves: lowest frequencies and longest wavelength

Question 10

Explain how microwaves are different to sound waves (4)

Answer 10

• sound waves cannot travel through a vacuum / microwaves can travel through a vacuum
• sound waves are slower / microwaves can travel at speed of light
• sound waves are longitudinal / microwaves are transverse
• sound waves have lower frequencies / microwaves have
higher frequencies

Question 11

Compare light waves and sound waves (4)

Answer 11

Similarities: • both can be reflected • both can be refracted • both can be diffracted • both interfere • both transfer energy
Differences: • light can travel through a vacuum • sound cannot travel through a vacuum • different speed / velocity • one is longitudinal, and one is transverse • accept light is faster than sound
Allow correct description: • (longitudinal) the oscillations / vibrations are parallel to / same direction as (the direction of energy transfer)
• (transverse) the oscillations / vibrations are 90° to / perpendicular to (the direction of energy transfer) • sound is a mechanical wave / caused by vibrations and light is an electromagnetic wave

Question 12

Compare Diffuse & Specular Reflection (3)

Answer 12

Specular Reflection:
• type of reflection where all the waves have the same angle of reflection and angle of incidence
Diffuse Reflection:
• where the waves are all reflected at different angles

Question 13

Explain why there is refraction at the boundary between air and glass (2)

Answer 13

• light travels more slowly in the glass block than in the air
• so light ray changes direction

Question 14

Compare a real image and a virtual image (4)

Answer 14

• Real image can be put on a screen
• Real image is on the opposite side of the lens to the object
• Virtual image cannot be put on a screen / film
• Virtual image is imaginary
• Virtual image is where virtual rays (seem to) come from
• Virtual image formed where virtual rays intersect / cross

Question 15

Describe what is meant when an obiect is described as a perfect black body (3)

Answer 15

• the object absorbs all the radiation transmitted on it
• the object does not reflect or transmit any radiation
• the object is the best possible emitter of radiation

Question 16

What is echo sounding used for, and what is measured when the reflected sound waves are detected? (3)

Answer 16

• measuring the depth of water below ships / detecting obiects in deep water
• time taken by each high-frequency sound wave
• travel from the sea-bed and back to the detector

Question 17

Describe how an image is created when ultrasound waves meet a boundary between different materials and explain the risk of carrying out ultrasound scans on unborn babies (4)

Answer 17

• ultrasound/waves partially reflected at different tissue/substances
• time taken to return is measured and used to produce image
• no risk / no danger
• ultrasound is not ionising / does not damage cells
• no precautions need to be taken

Question 18

Describe how stars are formed (4)

Answer 18

• nebula / dust and gas pulled together by gravitational attraction/force
• protostar begins to glow when hot enough
• star is formed when hot enough for nuclear fusion
• hydrogen nuclei fuse together to form helium nuclei releasing large amounts of energy

Question 19

Describe how the Universe has a large variety of different elements (4)

Answer 19

• hydrogen nuclei fuse together to form helium nuclei
• nuclear fusion in stars forms heavier elements
• supernova forms elements heavier than iron
• heavy elements scattered throughout Universe by supernova

Question 20

State the differences between a main-sequence star and a protostar (3)

Answer 20

• nuclear fusion happens in main-sequence star / nuclear
fusion does not happen in protostar
• main-sequence star is hotter / protostar is cooler/less
hot/lower temperature
• main-sequence star emits more radiation

Question 21

Explain why our Sun is stable (3)

Answer 21

• nuclear fusion in the core causes outward force of radiation
pressure
• balanced by inward force of gravity
• when forces are equal there is an equilibrium

Question 22

Explain what causes our Sun to become a red giant (6)

Answer 22

• when most of the hydrogen in the core has become helium
• there is no longer enough nuclear fusion of hydrogen
• so the outward radiation pressure decreases
• gravitational forces causing inward contraction are now stronger
• core collapses in on itself
• outer layers then expand (swell out) to form a red giant

Question 23

Explain how a red giant becomes a white dwarf (3)

Answer 23

• no more fusion in the core of a red giant means no more outward radiation pressure
• so the red giant collapses in on itself due to its own gravity
• as the collapse happens, it heats up becoming white, emitting some light.

Question 24

If a satellite is orbiting Earth, explain why the velocity is constantly changing (3)

Answer 24

• satellite accelerates due to force of gravity
• acceleration causes change in direction
• change in direction means velocity has changed

Question 25

Describe what needs to happen to a satellite falling towards Earth to have a new stable orbit (2)

Answer 25

• if the satellite gains speed as it falls and then remains constant
• new lower orbit will be achieved

Question 26

Explain how red shift supports the Big
Bang theory (4)

Answer 26

• galaxies furthest away have the largest red shift
• galaxies furthest are away are moving fastest/quickest
• this tells us the Universe is expanding
• Universe originated from single dense point

Question 27

What is expected to happen to the wavelength of CMBR in billions of years time and how has the CMBR been mapped out? (4)

Answer 27

• universe will continue to expand
• causing the wavelength of the microwaves to increase / become radio waves
• microwave detectors on Earth
• satellites in space

Question 28

Describe how two bar magnets can be used to demonstrate a force of attraction and a force of repulsion (3)

Answer 28

• bring two unlike poles close together
• magnets will attract due to force of attraction
• bring two like poles close together
• magnets will repel due to a force of repulsion

Question 29

Explain how you could show that a magnetic field has been produced around a current carrying wire (4)

Answer 29

• move a (magnetic / plotting) compass around the wire
• the changing direction of the compass needle shows a magnetic field has been produced
• sprinkle iron filings onto the card
• tapping the card will move the filings to show the magnetic field

Question 30

Two iron rods placed inside a solenoid with an open switch.
Explain why the iron rods move apart when the switch is closed (2)

Answer 30

• the rods become (induced) magnets
• with the same polarity (at each end)

Question 31

State three ways that would make the coil in a DC motor move faster (3)

Answer 31

• increase number of turns of wire on coil
• increase speed of coil
• strengthen magnetic field

Question 32

State two changes that would reverse the direction the coil in a DC motor spins (2)

Answer 32

• reverse direction of magnetic field
• reverse direction current flows
• reverse polarity of battery

Question 33

A relay switch can be operated by an
electromagnet. This type of switch is used in a car starter motor circuit.
Explain how turning the ignition key makes a current flow in the starter motor (4)

Answer 33

• Current flows through the coil (of the electromagnet)
• (Magnetic) field is produced
• The (iron) arm/pivot is attracted to the electromagnet
• The contacts are pushed together
• Current flows in starter motor

Question 34

A door lock controlled by an electromagnet can be opened from a flat inside a building.
Explain how the door is unlocked when the switch is closed (4)

Answer 34

• current flows coil
• electromagnet activated magnetic field produced
• attracts iron bar causing bolt to be pulled out

Question 35

what is an electromagentic?

Answer 35

A solenoid with an iron core