Topic 9: Wave phenomena

Question 1

Describe the conditions required for an object to perform simple harmonic motion (SHM).

Answer 1

The acceleration is proportional to the displacement and in the opposite direction (acceleration ∝ -displacement)

Question 2

T = 2π √(m/k)

Answer 2

T = time period (s)
m = mass (kg)
k = spring constant (N/m)

Question 3

If an identical spring is placed in parallel and a spring-mass simple harmonic motion experiment is repeated, suggest how this change would affect the fractional uncertainty in the mass of the block.

Answer 3

• When another spring is added in parallel, the forces produced by the two springs are added together (the spring constants are added together)
• A greater overall spring constant means a lower time period
• Fractional uncertainty in time period would increase as the absolute uncertainty is constant but the value is decreasing
• Mass is directly proportional to the time period so therefore, the fractional uncertainty in the mass would decrease for the same reason

Question 4

When a source is moving towards a stationary observer, what can be said about the frequency?

Answer 4

Higher frequency

Question 5

When a source is moving away from a stationary observer, what can be said about the frequency?

Answer 5

Lower frequency