General questions and answers from past papers

Question 1

What is the significance of the decay constant?

Answer 1

the probability per second; of a decay / change of a (single) nucleus/atom

Question 2

How to find the relative velocity with momentum=

Answer 2

(P) momentum initial
(P) momentum final = initial - change in momentum
v =p/m

Question 3

How to find the observed factor of the particles moving (relativistic time dilation)

Answer 3

Times the rest factor by the relativistic time dilation factor

Question 4

Statement about satellites in a circular orbit

Answer 4

Its orbital path is on an equipotential surface

Question 5

Statements which provide evidence the universe came from the big bang

Answer 5

Microwave radiation from the Universe can be detected in all directions.
The red-shift of lines in a galaxy’s spectrum is proportional to its distance from our galaxy.

Question 6

Heat increasing the internal energy and pressure
of the gas, explain the increase in pressure in terms of changes in the motion of the particles in the
gas.

Answer 6

• Increased their speed/velocity;
• Greater momentum change per collision (with the walls);
• Increases rate of collisions (with walls)

Question 7

Explain why the internal energy of the gas decreases when a gas expands a container.

Answer 7

work done by gas; equals decrease in internal energy

Question 8

Describe how electromagnetic waves can be used to measure the distance of the Moon from the surface of the Earth. State an assumption which has to be made about
electromagnetic waves.

Answer 8

-Pulses of light/microwaves from Earth reflect from
the Moon;
-speed of light x half the pulse-echo time = distance
-assumes: speed of light (or EM waves) same all the way through the journey / same time for both halves of journey

Question 9

Explain why this acceleration does not change the speed of the Moon in its orbit around the Earth.

Answer 9

Acceleration / force is at right angles to displacement / velocity so no work is done

Question 10

Why is the field strength smaller or 0 nearer the moon

Answer 10

This is where the field strengths cancel out; because the moon is less massive than the earth, the point where they cancel needs to be closer to the moon for an equal field strength