explanations

Question 1

by considering energy,

why is the p.d. < emf of battery

Answer 1

• Emf is total energy available per unit charge

- Energy is dissipated in the internal resistance

Question 2

explain how a single beam of alpha particles and gamma radiation may be separated

Answer 2

• Electric field is used at an angle to the beam
• Alpha particles will show deflection
• Gamma radiation will show no deflection

Question 3

conditions for formation if stationary waves

Answer 3

• two waves with the same frequency, wavelength, and speed but in opposite in direction overlap

Question 4

projectile motion –> why is KE of ball not equal to GPE

Answer 4

• there is KE of the ball when it starts its path

Question 5

explain how the collision is inelastic but still obeys the law of conservation of energy

Answer 5

• kinetic energy not conserved

- but total energy is conserved

Question 6

explain the part played by diffraction in the production of the fringes

Answer 6

• when the waves passes the slit, they spread into
  geometrical shadows
• and interfere

Question 7

why double-slit used instead of two sources of light

Answer 7

• double slit produces two coherent waves with constant

phase difference

Question 8

describe 2 diff between Beta- emission and Beta+ emission

Answer 8

• During B- emission, anti-neutrino also emitted,
  During B+ emission, neutrino also emitted
• During B- emission, neutron changes into proton
  During B+ emission, proton changes into neutron

Question 9

Describe and Explain how the change in KE of Alpha-particles compares with Electrons

Answer 9

• charge of alpha particles is positive, opposite to
  electron
• KE is reduced
• charge of alpha-praticles is twice than that of electrons,
• KE is twice

Question 10

By reference to interference,
1. Explain the zero order maximum

2. First order maximum

Answer 10

1. Waves overlap with phase difference of 0

2. Waves overlap with phase difference of 360

Question 11

Describe I-V graph of
1. A metallic conductor at constant temp

2. A semiconductor diode

Answer 11

1. • Straight line through the origin
2. • 0 current for one direction, up to 0 or few tenths of
     volts in the opposite direction
   • straight line with positive gradient

Question 12

explain what is it meant by charge is ‘quantised’

Answer 12

charge exists only in discrete amounts.

Question 13

differences between stationary waves and progressive waves

Answer 13

1. -progressive wave transfer energy,
   -stationary wave does not
2. -in progressive wave, all particles have same
   amplitude
   -in stationary wave, amplitude varies from max to
   min/zero
3. -in progressive wave, adjacent particles are not in
   phase
   -in stat; adjacent particles are in phase

Question 14

explain how the motion of the oil drop shows that it is in equilibrium.

Answer 14

• oil drop is in constant speed

- so no Rf

Question 15

Describe the change to the pattern of the field lines (lines of force) representing the uniform electric field as the potential difference decreases

Answer 15

• separation of field lines increases

Question 16

conditions for ripple tank waves to be visible

Answer 16

• coherent

- same amplitude

Question 17

name a piece of equipment to allow waves in the ripple tank to be seen clearly

Answer 17

stroboscope to free the motion of the waves

Question 18

Explain why an intensity maximum is detected at C

Answer 18

• Path Difference = resultant distance/wavelength = nλ
• Waves are IN PHASE with each other
• Constructive Rnterference takes place with maximum
  intensity

Question 19

Describe how measurements can be taken to determine accurately the cross-sectional area of the wire.

Answer 19

• Using a micrometer,
• measure the diameter of wire
• take several readings along the wire and average

Question 20

suggest why B- particles are emitted with a range of kinetic energies

Answer 20

• antineutrinos are also emitted

- KE shared with antineutrinos

Question 21

Explain the origin of upthrust

Answer 21

• there is a difference in pressures on the top and bottom
  surfaces of the cylinder
• pressure bottom > pressure top

Question 22

uncertainty of micrometer vs metre rule

Answer 22

micrometer +/- 0.01mm

metre rule. +/- 1mm

Question 23

angle constant, frictional force constant.

Explain why is it incorrect to assume the total resistive force is constant

Answer 23

• force due to air resistance is not constant

- air resistance ↑ as v ↑

Question 24

Part of the energy released by the decay is given to the 2 leptons.
State 2 possible forms of the remainder of the energy released.

Answer 24

• KE

- gamma radiation

Question 25

Describe the energy conversion that occurs when the parcel is falling through the air at constant (terminal) speed.

Answer 25

GPE –> Thermal Energy / internal

Question 26

when Ar is negligible, why is the horizontal component of velocity of the ball constant.

Answer 26

• force in horizontal direction is zero

Question 27

Explain why when the card has come to rest, its centre of gravity is vertically below point P

Answer 27

• line of action of weight acts through P

- so weight does not have a moment at P

Question 28

A greater mass is kicked with the same velocity
State and explain the effect, if any of the increased mass on the max height reached by ball. (Air resistance is negligible)

Answer 28

• no change to max height
• acceleration of ball is unchanged as it is not dependent
  of the mass

Question 29

Explain why a bright fringe is produced at X

Answer 29

• Waves from slit overlap at X
• With phase diff of 0 degrees
• ## Constructive Interference takes place

Question 30

State 3 quantities that are conserved in the decay

Answer 30

• mass energy
• charge
• proton number
• nucleon number

Question 31

what is meant by the particles colliding elastically

Answer 31

• total KE before collision = total KE after collision

Question 32

Suggest why the B- particles are emitted with range of kinetic energies

Answer 32

• anti-neutrinos are also emitted

- energy is shared with anti-neutrinos