2020 Paper 3 (24/03/2025)

Question 1

Placing fiducial marker for pendulum practical?

Answer 1

Place the centre of the marker in line with either edge of the pendulum bob. This is because the pendulum is moving fastest and has its maximum kinetic energy at this position and transit time is the least

Question 2

Finding maximum amplitude of the pendulum experimentally?

Answer 2

Have a horizontal scale and have a set square, as its a form of equipment which eliminates parallax error, at equilibrium position and at maximum displacement, from edge of bob, and subtract the readings.

Question 3

Absolute Uncertainty in mean?

Answer 3

1/2 the value of the range

Question 4

Random Error?

Answer 4

Random errors cause readings to spread out about the true value due to results varying in an unpredictable way

Question 5

Thinner material in Young’s Modulus practical?

Answer 5

Advantage: Same load produces larger values of displacement meaning the uncertainty in this value decreases
Disadvantage: Plastic deformation could occur meaning graph may become no linear and this affects graph with issues like scatter and reduces range of m. As well there is safety concern with things like beam potentially breaking

Question 6

Reading a vernier scale?

Answer 6

Where the 0 lines up is the main value, where the moving scale lines up is the decimal places of the value the main value has lined up with

Question 7

Order of magnitude?

Answer 7

This is the number of significant figures an answer rounds to?

Question 8

EMF investigation?

Answer 8

Record and measure voltage and current readings and adjust resistance on variable resistor and repeat readings. Then plot a voltage against current graph. EMF will be the y-intercept, and the negative value of the gradient will be equal to the internal resistance of the circuit

Question 9

Voltmeter in EMF Investigation?

Answer 9

It is located in parallel to the battery

Question 10

Comparing Power and telescope comparison?

Answer 10

Telescopes can be compared using collecting power in the following relationship and give a ratio which can be evaluated: collecting power ∝ area otherwise collecting power ∝ diameter squared as all other terms in areas will be the same

Question 11

Problems with refracting telescopes?

Answer 11

They can suffer chromatic and spherical aberration. They are heavier and longer than reflective telescopes.

Question 12

Problems with reflecting telescopes?

Answer 12

The secondary mirror blocks some of the incoming light which can reduce its brightness and can have effects from diffraction

Question 13

Distance is absolute and apparent magnitude equation?

Answer 13

This distance in: m - M = 5 log d/10 has its units in parsecs

Question 14

Evolution of supergiant?

Answer 14

The evolution of a super giant will either cause a supernovae collapse or will form into a neuron star or black hole. These evolutions will result in a gamma ray burst

Question 15

Data needed and used to find Hubble’s Constant?

Answer 15

The data needed is recessional velocity, red shift, known distances to things like supernovae and the wavelength of spectral lines. This will give information allowing graph of velocity in kms-1 on y-axis and distance in megaparsecs to be blotted where Hubble’s constant is the gradient

Question 16

Limitation of finding Hubble constant graphically?

Answer 16

Values of apparent magnitude will be affected by what the light passes through. Much variation in data whether that be variations between galaxies or random error in measurement. At large distances accelerating universe will affect graph. Lots of data from supernovae is needed.