Questions I Got Wrong In Papers Flashcards
Explain why the acceleration does not change the speed of the Moon in its orbit around the Earth.
Acceleration/gravitational force is at right angles to velocity so no work is done on the velocity.
What is the significance of the decay constant?
The decay constant measures how quickly an isotope will decay. It is the probability of a given nucleus decaying in a certain time.
A gas particle takes a few minutes to travel a metre through air, why is this?
-gas particles change direction. - because they collide with other particles. - ignore description of random walk.
A tyre has 3x10^24 air particles at a temperature of 280k. Find the internal energy.
3x10^24 x 280 x 1.4 x 10^-23 = 11760J
Explain how an astronomer could use the wavelength of a single radar echo to confirm the measurement of the asteroids component of velocity towards Earth.
- measure change in wavelength - apply z = ^¥/¥ = v/c - measure blueshift.
Draw V vs T for a harmonic oscillator then draw A vs T on the same graph.
Page 12 of revision guide.
What feature of the diagram shows that the electric field strength is strongest near the wire?
- The fact that the equipotentials are getting closer together the closer to the cable they get.
This question is about muons. These particles are formed as cosmic rays enter the upper atmosphere.
A negatively charged muon decays in the following manner.
muon ⇒ electron + neutrino + antineutrino
Explain how the decay equation above shows that this muon is a negatively-charged lepton.(2)
Lepton number conserved(1)
Charge number conserved(1)
Use the relationship between induced emf and rate of change of flux to explain why the induced emf in the secondary coil is zero when the current in the primary coil is a maximum.
Any two from:
Induced emf is zero when (rate of) change of flux is zero(1)
(rate of change of)flux is proportional to(rate of change of ) current.(1)
Rate of change of flux or current is zero at maximum(1)
A laminated core is replaced with a solid core of the same material. Nothing else is change. It is observed that the maximum emf across the secondary coil is now lower than that with the laminated core. Explain why this is the case.
- Max two marks from:
- Larger eddy currents
- Eddy currents set up flux
- Eddy currents produce energy losses.
And max two marks from:
- Maximum flux reduced.
- When max flux reduced the max rate of change of flux is also reduced.
In the equation pV = 1/3Nmc2 what is m the measure of? what is N a measure of?
m is the measure of the mass(in kg) of one gas particle. N is the a measure of the number of particles in the gas.
What property of light is measured to determine the red-shift of a galaxy?
(shift of) wavelength of (absorption) lines in spectrum of a galaxy.
Explain how cosmological red shift provides evidence for the “big bang”.
(redshift means) universe is expanding / galaxies are moving away from each other / velocity away us increases with increasing distance; therefore universe / galaxies / stars were at the same point far enough back in time;
any of the following:
[1] each, maximum [3]
-air acts like a spring because: as volume decreases pressure increases because pV is constant (= NkT) -more collisions as particles pushed together -increased transfer of momentum to cone from particles force from particle impacts restores cone to equilibrium position any of the following
[1] each, maximum [3]
effects on the frequency: total k increases spring and air act in parallel frequency of free oscillations increases
Explain why muons travelling at very high speeds in a beam decay slower than if they were not travelling in the beam.
time dilation occurs / muon time runs slower than laboratory time / effective half-life longer for muons
