Question

The figure shows a wave generated in 0.2 s. Its speed is:

• A. 400 m/s
• B. 40 m/s
• C. 4 m/s
• D. 0.4 m/s

Answer 1

Answer:

B. 40 m/s

The figure shows a wave generated in 0.2 s. Its speed is:

Based on the provided figure and information, the speed of the wave is 40 m/s.

To find the wave speed, you need to determine its wavelength and frequency.

1. Find the Wavelength (λ)

A wavelength is the distance over which the wave's shape repeats. From the figure, the horizontal distance shown is 8 m, which contains 2 full cycles (or waves).

• 1 cycle is from one peak to the next or one trough to the next.

• The diagram shows 4 crests (peaks) and 3 troughs (low points). This is equivalent to 3.5 cycles.

• The distance for 2 cycles is 8m.

• So, the distance of one cycle, the wavelength (λ), is:

  • λ=Number of CyclesTotal Distance​=28 m​=4 m

2. Find the Frequency (f)

Frequency is the number of cycles per unit of time. The figure states that the wave was generated in 0.2 s.

• The wave has 2 cycles in 0.2 s.

• So, the frequency (f) is:

  • f=TimeNumber of Cycles​=0.2 s2​=10 Hz

3. Calculate the Wave Speed (v)

The speed of a wave is calculated using the formula:

• v=f×λ

• v=10 Hz×4 m=40 m/s

The 10 cm dimension on the vertical axis represents the amplitude of the wave and is not needed to calculate the speed.