Past Paper Improvements

Question 1

When making an estimate, what is the most important thing to remember?

Answer 1

Your answer cannot be to a greater number of significant figures than the values used to calculate it. i.e, if you are provided with data to 2 significant figures, your estimate should be to 2 significant figures

Question 1

Answer 1

B

Question 2

What must you remember when looking at the doppler shift of emission/absorption spectra?

Answer 2

The shift in wavelength is different for each line. “Δλ/λ = v/c”, therefore the change in wavelength is dependent on the orginal wavelength. The spectrum will not look as though it has just been shifted along, but rather stretched as the longer wavelengths will be shifted by a greater amount

Question 3

How can you accurately use a thermometer?

Answer 3

Stir (if in a fluid) and avoid parallax error

Question 4

What do you call the divisions/increments on a measuring instrument?

Answer 4

The resolution

NOT THE PRECISION OR ACCURACY

Question 5

Which scale would you use on this pressure gauge and why?

Answer 5

The psi scale as the resolution is much higher than the kPa scale. The divisions/increments are far smaller

Question 6

Why does mercury have no atmosphere but pluto still has a thing atmosphere?

Answer 6

Mercury has a higher escape velocity than Pluto (4.2 km s⁻¹ compared to 1.2 km s⁻¹). However, Mercury is far closer to sun and is therefore hotter. As a result the molecules on Mercury (are more likely to) have speed higher
than the escape velocity and therefore Pluto still has a thin atmosphere whilst mercury does not.

Question 7

Explain why weight and normal contact force are not examples of newtons third law:

Answer 7

• They are different types of forces, one is gravitational and the other is electrostatic
• They both act on the same object, the pair of forces should act on 2 different objects

Question 8

What do error bars on a graph show?

Answer 8

ABSOLUTE uncertainty

NOT error

Question 8

Why are hydrogen spectral lines often used to measure a star’s velocity?

Answer 8

• Hydrogen is most common element in stars and therefore has most intense (spectral) lines.
• The intensity of light from other elements may be too low for accurate measurement.

Question 9

What are the important factors of CMBR?

Answer 9

• Formed as gamma radiation during the Big Bang
• Galactic red shift to microwave wavelength
• Intensity is uniform in all directions
• Corresponds to a temperature of 2.7K