AP Physics Physics: Thermodynamics & Modern Physics 5

Question 1

The mass defect of a nucleus is directly related to its:

Accepted Answer

Binding energy

Answer

Binding energy = mass defect × c²; the mass defect represents the energy needed to completely separate the nucleus into its constituent nucleons.

Question 2

Which of the following correctly describes the relationship between absolute temperature T and the average kinetic energy of molecules in an ideal gas?

Accepted Answer

KE_avg = (3/2)kT

Answer

From the kinetic theory of ideal gases, the average translational kinetic energy per molecule is (3/2)k_B T.

Question 3

Alpha particles are deflected significantly by electric and magnetic fields because they:

Accepted Answer

Carry a charge of +2e

Answer

Alpha particles consist of 2 protons and 2 neutrons, giving them a charge of +2e, which causes deflection in fields.

Question 4

A refrigerator removes 800 J of heat from a cold interior and expels 1100 J to the warm exterior. How much work does the refrigerator's compressor do?

Accepted Answer

300 J

Answer

By energy conservation: W = Q_hot - Q_cold = 1100 J - 800 J = 300 J of work input required.

Question 5

What happens to the wavelength of a photon when it passes through a gravitational field (gravitational redshift)?

Accepted Answer

It increases as it escapes a gravitational well

Answer

Photons lose energy climbing out of a gravitational well, decreasing frequency and increasing wavelength — this is gravitational redshift.

AP Practice Test

AP Practice Test

AP Physics Physics: Thermodynamics & Modern Physics 5