Problems
practice
- How about a simple, straightforward problem?
- Compute the rms speed of an oxygen molecule at room temperature.
- Use the results of part a. to determine the rms speed of a hydrogen molecule at room temperature.
- Use the results of part b. to determine the rms speed of a mercury atom at 1200 K.
- Write something else.
- Write something different.
- Derive the law of Dulong and Petit by applying the equipartition of energy to the atoms in a solid.
numerical
- What is the rms speed of a hydrogen atom in the interplanetary medium (the thin, cold plasma between the planets) if it has a temperature of 16 K?
- What is the speed of a typical free electron in copper at room temperature? (Free electrons in a metal are those which are so loosely bound that they wander from atom to atom like the molecules in a gas.)
- Weapons grade uranium is enriched by the diffusion of gaseous uranium hexafluoride (UF6) through a stack of tight metal screens. The lighter, fissionable isotope 235U has a slightly faster rms speed and is more likely to diffuse through the screens than the heavier, non-fissionable isotope 238U. Determine the ratio of the rms speed of UF6 made from the light, desirable isotope to the heavier, undesirable isotope.
- A lead bullet weighs 4.5 g and is fired from a rifle at 914 m/s. The propellant heats the bullet to 50 °C. Determine the following quantities…
- the kinetic energy of the bullet
- the number of moles of lead in the bullet
- the total internal kinetic energy of the bullet
- the rms speed of the lead atoms in the bullet
- A 1 m3 box contains 1 mol of helium at 727 °C. The box sits in a standard temperature and pressure (STP) environment. The box is airtight, but not thermally isolated (that is, heat can flow through the walls of the box). The box has a door on it that can open inward or outward when the airtight seal is broken.
- Determine…
- the rms speed of the helium atoms in the box
- the total internal energy of the helium atoms in the box
- the pressure on the inside walls of the box
- Is the net direction of heat flow into or out of the box? Justify your answer.
- Will the door on the box swing inward or outward when the seal is broken? Justify your answer.
- In 2015, physicists at Stanford University in California set a new record low temperature — an ensemble of 100,000 rubidium atoms cooled to 50 pK. Determine…
- the rms speed of the atoms
- the total internal energy of the ensemble