Bennett Mechanical Acoustics and Optics Questions and Answers

Question 1

A person stands 100 meters from a large, flat cliff face and shouts.
They hear an echo shortly after.
If the person then walks 50 meters closer to the cliff and shouts again, what will happen to the time it takes to hear the echo?

Accepted Answer

The time will be halved.

Answer

The time will be doubled.

Answer

The time will remain the same.

Answer

The time will be quartered.

Question 2

A person is standing on the bank of a clear, still pond and wants to spear a fish that they see in the water. Due to an optical effect, the fish is not where it appears to be. Where should the person aim to hit the fish?

Accepted Answer

Slightly below the apparent location of the fish.

Answer

Directly at the apparent location of the fish.

Answer

Slightly above the apparent location of the fish.

Answer

To the left or right of the apparent location.

Question 3

A mechanic is working in a large garage with concrete walls and floors, and the sound of the tools is creating a loud echo. Which of the following changes would be most effective at reducing the echo?

Accepted Answer

Hanging heavy fabric curtains or acoustic foam panels on the walls.

Answer

Painting the walls with glossy paint.

Answer

Installing large glass windows.

Answer

Replacing the concrete floor with polished tile.

Question 4

You are standing still on a sidewalk as an ambulance with its siren on approaches you, passes you, and then moves away. How does the pitch of the siren you hear change?

Accepted Answer

The pitch is high as it approaches and low as it moves away.

Answer

The pitch is low as it approaches and high as it moves away.

Answer

The pitch continuously gets lower from the moment you first hear it.

Answer

The pitch remains constant the entire time.

Question 5

Which of the following optical devices is most suitable for concentrating sunlight to a single point to start a fire?

Accepted Answer

A convex lens.

Answer

A concave lens.

Answer

A flat pane of glass.

Answer

A plane mirror.

Question 6

If you hold a sign with the word 'PHYSICS' printed on it up to a standard flat mirror, how will the word appear in the reflection?

Accepted Answer

SↃIƧYHꟼ

Answer

PHYSICS

Answer

ԀHʎSIƆS

Answer

SCISYHP