Worksheet: Brownian Motion

In this worksheet, we will practice describing the Brownian motion of particles and how this explains the diffusion of gases.

Q1:

Which of the following objects’ motion best represents Brownian motion?

  • A
  • B
  • C
  • D
  • E

Q2:

If an object exhibits Brownian motion that has an average speed of 1.2 cm/s, which of the following is most likely to be the magnitude of its displacement after 60 s?

Q3:

A gas consists of a very large number of particles that are in Brownian motion. Which of the following most correctly relates the most likely speed of a particle in a gas to the direction of its motion?

  • AThe more particles in the gas moving in the opposite direction to the particle, the smaller its speed is likely to be.
  • BThe more particles in the gas moving in the same direction as the particle, the greater its speed is likely to be.
  • CThe speed of a particle is independent of the direction of its motion.
  • DThe more particles in the gas moving in the same direction as the particle, the smaller its speed is likely to be.
  • EThe more particles in the gas moving in the opposite direction to the particle, the greater its speed is likely to be.

Q4:

The container shown in the diagram consists of two equally-sized chambers. The chambers hold two different gases, both at the same temperature. The particles of both gases undergo Brownian motion. The separating wall between the chambers is removed. Which of the following most correctly represents the distribution of the particles of the gases a few minutes after the separating wall has been removed?

  • A
  • B
  • C
  • D
  • E

Q5:

Which of the following most correctly explains the Brownian motion of objects?

  • AAn object in Brownian motion has no net force acting on it.
  • BAn object in Brownian motion is attracted to its initial position, so its net displacement over time is zero.
  • CAn object in Brownian motion collides repeatedly with other objects, each of which moves independently of the other.
  • DAn object in Brownian motion collides perfectly elastically with anything that it contacts, so it always tends to return to its initial position.
  • EAn object in Brownian motion has a constant mechanical energy, so its net displacement over time is zero.

Q6:

What type of motion most correctly describes the translational motion of a particle in a gas over a time interval of a few seconds?

  • ABrownian motion
  • BCircular motion
  • CUniform motion
  • DPeriodic motion
  • ESimple harmonic motion

Q7:

The object shown moves with Brownian motion between the points shown at the instants 𝑡, 𝑡, and 𝑡. Which of the directions shown is the object most likely to move in after 𝑡?

  • AIV
  • BIII
  • CI
  • DAll directions are equally likely.
  • EII

Q8:

A very small object moves with Brownian motion as it passes through a region containing gas particles. The path of the object is shown in the diagram. Which of the following most correctly represents the distribution of gas particles in the region?

  • A
  • B
  • C
  • D
  • E

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