Exam Question Answer Structure

Question 1

Explain (using the graph) whether the object obeys Hooke’s Law

Answer 1

• constant gradient
• passes through zero
• extension is proportional to force

Question 2

What is the centre of gravity

Answer 2

the point at which all the weight of an object can be assumed to act

Question 3

State a simple method to test the centre of gravity of an object

Answer 3

balance the object on a finger/pivot at this point and see if it stays balanced and level

Question 4

Suggest why the drag is so much greater than the Stoke’s law force

Answer 4

because Stoke’s law relies only on laminar flow

Question 5

Temperature and viscosity

Answer 5

as the temperature increases the viscosity lessens so the ‘material’ flows more and is easier to spread

Question 6

State what is meant by work done

Answer 6

work done = force x distance moved in direction of the force

Question 7

State what is the difference between the stress above and below …

Answer 7

when below the stress is tensile, when above the stress is compressive

Question 8

Describe what is meant by plane polarised light

Answer 8

light only oscillates in one plane/direction, all other light is blocked if not oscillating in that plane, the plane includes the direction of travel

Question 9

Explain longitudinal waves

Answer 9

oscillations occur parallel to the direction of wave propagation/travel creating compressions and rarefactions

Question 10

What is ultrasound

Answer 10

frequency greater than 20000 Hertz

Question 11

Why is ultrasound emitted in pulses

Answer 11

so it has time between pulses for the previous pulse to return before the next one is sent; so we know which echo is from each pulse

Question 12

property of x-rays

Answer 12

ionising

Question 13

difference between x-rays and ultrasound

Answer 13

• x-rays transverse, ultrasound longitudinal
• x-rays travel in a vacuum, ultrasound doesn’t
• x-rays electromagnetic, ultrasound mechanical

Question 14

Explain what is meant by unpolarised

Answer 14

• oscillations occur in every directions

- perpendicular to the direction of wave travel

Question 15

Explain what is meant by a photon

Answer 15

a concentrated packet of electromagnetic energy

Question 16

Explain what is meant by threshold frequency

Answer 16

the minimum amount of energy (frequency) needed to release the photon from the surface of the metal. Only at this frequency or above will photons be emitted, one photon is absorbed by one electron, E = hf

Question 17

State what is meant by drift velocity

Answer 17

mean velocity of charge carriers

Question 18

State what is meant by refraction

Answer 18

as light passes a boundary through substances of different densities it causes a change in speed which causes a change in direction

Question 19

Total Internal Reflection

Answer 19

when the incident angle of light is greater than the critical angle all light is refracted so much it stays inside a tube/ball

Question 20

Superposition

Answer 20

when two waves pass through each other and the amplitudes sum (constructive) or subtract (destructive) creating nodes and antinodes

Question 21

Diffraction

Answer 21

spreading out of waves as they pass through a gap - maximum diffraction occurs when the size of the gap is similar to the size of the wavelength

Question 22

Explain why microwave/ other radiation could be dangerous

Answer 22

human body contains water so would gain heat

is ionising

Question 23

Photoube/Photoelectric effect

Answer 23

• electrons in metal plate absorb photon energy
• then they flow round a circuit to positive charge
• photon energy depends on frequency, photons must have more than the threshold frequency
• one photon can transfer energy to a single electron
• light with a greater intensity supplies more photons per second so more electrons can be emitted per second causing a greater current

Question 24

Why use a data logger

Answer 24

• higher sampling rate
• ensure the readings are simultaneous
• take more readings in a shorter time interval

Question 25

Explain 2 precautions the student should take to ensure accurate results

Answer 25

• switch off between readings so no heaing effect
• no zero error
• no parallax error
• no systematic error

Question 26

Conserved in a reaction

Answer 26

• charge
• momentum
• baryon number
• mass

Question 27

Faraday’s law of induction

Answer 27

induced EMF is proportional to the rate of change of flux linkage