Physics knowledge (relationships and definitions)

What can we change ½ m(m.s speed) = 3/2 x kT into to find molar mass?

½ M(m.s speed) = 3/2 RT where M is the molar mass

What happens to the resistance of a NTC thermistor when the temperature increases?

As temperature increases, the resistance decreases (opposite)

What happens to a thermistor’s resistance when the temperature increases?

When temperature increases, resistance increases (same)

What is newton’s 3rd law?

If an object exerts a force onto another object, then the other object exerts an equal and opposite force onto the original object.

What is the definition for gravitational potential energy?

The work done to bring an object from infinity to that point

What is the definition for gravitational potential?

The work done per unit mass to bring an object from a point in that field to infinity.

Describe the internal energy of an ideal gas

Internal energy only consists of kinetic energy since electrostatic forces (potential energy) is assumed to be negligible between the particles

What is the right hand rule used for?

It is used for determining the direction of the magnetic field around a current (from wire or charged particles)

What is the left hand rule used for?

F = BIL, the thumb is the force/direction of movement, the 1st finger is the direction of the magnetic field and the 2nd finger is the direction of the current.

What is faraday’s law?

When a change in magnetic flux linkage is created, an EMF is induced.

What is Lenz’s law?

The direction of the current/EMF of the change in magnetic flux is opposite to the change that created it.

What is centripetal force?

The resultant force that acts towards the center of an object in circular motion

What is red shift?

When light from a distance galaxy is shifted towards the red end of the spectrum. This indicates the galaxy is moving away from us since the distance has gotten larger

What is blue shift?

When light from a distant galaxy is shifted towards the blue end of the spectrum, indicating the galaxy is moving closer to us since the distance has gotten shorter

How is an emission line produced?

Electrons transition to lower energy levels which emits a photon of specific wavelength, corresponding to the difference in energy levels.

When a substance is increasing in temperature, explain the changes to internal energy?

Kinetic energy is increasing and potential energy stays the same.

What is the definition for internal energy?

The sum of the randomly distributed kinetic and potential energies within the molecules of a substance.

Describe the changes to the internal energy of a substance changing state

Kinetic energy stays the same and potential energy increases (becomes less negative)

What is the definition for absolute zero?

Absolute zero is when the molecules of a substance have no kinetic energy and minimal potential energy. It’s known value is 0K or -273 degrees.

What are the rules of a series circuit?

• Current is the same at any point

• Potential difference is split between the components

• Resistance is added

What are the rules of a parallel circuit?

• Current splits at branches (Kirchhoff’’s 1st law)

• Potential difference is the same in each branch

• Resistance is 1/R(total) = 1/R1 +1/R2 + …..

What are the rules for capacitors within circuits?

• In parallel, capacitance is added

• In series, capacitance is 1/C(total) = 1/C1 + 1/C2 + …

What is intensity proportional to?

Amplitude squared

What is kWh a unit of?

Energy

What is the principle of superposition of waves?

When two or more waves meet at a point in space, resultant displacement is equal tot he sum of the individual displacements

What is the definition of electric potential?

The energy required to move a positive charge within a field from a point to infinity

How do we prove that the mean density of all nuclei are roughly the same?

Mass of nucleus is proportional to A^1/3 (nucleon number)

Volume of nucleus is proportional to r^3 (radius)

Use P=m/V to show density is the same

Describe the force acting on an object when it is at it’s maximum height

The only force that is acting on the ball is it’s weight

how to find percentage uncertainty of multiple measurements?

• take mean of the values, excluding any outliers

• Find range of the values (with outliers excluded) and divide range by 2 (this is your uncertainty)

• Divide the uncertainty by the mean and multiply by 100 to get percentage.

How to find uncertainty of multiple measurements?

• take mean of the values, excluding any outliers

• Find range of the values (with outliers excluded) and divide range by 2 (this is your uncertainty)

What are the features of a geostationary orbit?

• They have a period of 1 day

• The move in the same direction as the Earth’s rotation

• They observe the same point of Earth’s surface at any time

• They have an equatorial orbit

How do you work out the total energy of an object within an orbit?

Total energy is the sum of the kinetic and potential energy. For orbits, it can be calculated using the formula: E = K.E. + GPE. GPE should be negative since it is potential energy.

What is the definition of the luminosity of a star?

The total radiant power of a star

How is an absorption line produced in terms of photons and electrons?

When electrons move to a lower energy level, a photon is produced with a specific wavelength that corresponds to the energy difference between the two levels. The photon is then detected and marked with a black line indicating its wavelength. This contrasts between the light colour of the wavelengths that are not absorbed within the spectrum.