Last Minute Physics flashcards

Read before entering the exam room

Newton’s universal law of gravitation

The force of gravity between two objects is inversely proportional to the square of the separation of their ceters and force is directly proportional to the product of their masses.

When do astronauts in space stations feel weightless?

The centrpetal force is the gravitational force between the earth and space station. Both the astronaut and the space station have the same acceleration. The acceleration is the ravitational field strength at that position.

What is the specific heat capacity of water

4200 J kg^-1 K^-1

Traverse waves and examples

They cause the medium to move perpendicular to the direction of the wave (examples: water waves and S earthquakes)

Longitudinal waves and examples

They cayse the direction of the particles to be parallel to the direction of the wave (eg. sound waves)

Why do a finite number of energy levels exists?

Photons are emitted in transitions of electrons from higher energy levels to lower energy levels (excitation) and because there are only a specific wavelength or energies emitted.

Snell’s law

a law stating that the ratio of the sines of the angles of incidence and refraction of a wave are constant when it passes between two given media.

Explain the role of convection in an air baloon

• The temperature increases due to convection currents.

• The hot balloon exapand and its density decreases below the air outside the balloon causing an upwards force, if it exceeds the weight then it’ll start floating

Relationship between emissivity and intensity

Emissivity is the ratio of intensities of two bodies

Which one has higher albedo, ice or sea?

High albedo scatters more visible radiation: Ice is a good reflector hence has a higher albedo whereas the sea is a good absorder so it has a low albedo.

What is the condition for a double slit

The waves should eb coherent, menaing that they have constant phase difference.

How to find intensity leaving

Sum of the intensity of the reflected Solar constant + outgoing thermal radiation

Momentum and force time graph

Constant area in the force time graph graph means constant increase in momentum

Power formula

P = Fv

Relationship between KE and amplitude

When the amplitude increases the KE decreases (negative direct proportion)

Relationship between acceleration and resultant force

Acceleration is proportiona to the resultant force so it is always in the same direction

Relationship between wavelength and the period

Wavelength ratio = period ratio

Speed of sound

travels faster in water over air

What is the process of nuclear fusion/fission

The joining/splitting of a nuclei, releasing energy

What is the transformation of elements when fusion occurs

hydrogen to helium

Which forces are balanced in a large stable sequence star?

gravity and radiative pressure

What elements are fused in the core of supergiants?

helium into heavier elements up to iron

What would be the stage of a supergiant star thats 10/30 times the sun

10 → neutron star

30 → black hole

What can be determined from the direct measurements of the spectrum of the star, without other data being required?

composition and surface temperature

What is the use of a fuel rod?

to absord neutrons

What is the use of the moderator?

To lower the kinetic energy of neutrons

Describe the daughter nuclei

Radioactive and have long half lives