A transverse wave given by $y = 2 \sin(0.01x + 30t)$ moves on a stretched string from one end to another end in $0.5\ \text{second}$. If '$x$' and '$y$' are in $\text{cm}$ and '$t$' is in $\text{second}$, then the length of the string is
Show Hint
Always double-check the measurement units specified in wave problems! Here, $x$ is given in centimeters, which means your initial velocity calculation yields $\text{cm/s}$. Skipping the conversion to meters per second can easily lead to a factor-of-100 error.
Step 1: Understanding the Question:
We are given the wave function equation for a progressive transverse wave propagating along a stretched string. The total travel time across the string length is given as $0.5\ \text{seconds}$. We need to compute the physical spatial length of this string. Step 2: Key Formula or Approach:
1. Compare the given equation with the standard progressive wave formula:
$$y = A \sin(kx + \omega t)$$
Where $k$ is the wave number and $\omega$ is the angular frequency.
2. The linear wave propagation speed ($v$) is given by the relation:
$$v = \frac{\omega}{k}$$
3. The total distance covered (length of the string, $L$) in time $t$ is:
$$L = v \cdot t$$
Step 3: Detailed Explanation:
From the provided wave equation $y = 2 \sin(0.01x + 30t)$:
The wave number coefficient of $x$ is $k = 0.01\ \text{cm}^{-1}$.
The angular frequency coefficient of $t$ is $\omega = 30\ \text{rad/s}$.
Let's compute the wave velocity $v$:
$$v = \frac{\omega}{k} = \frac{30}{0.01} = 3000\ \text{cm/s}$$
Convert this velocity value from centimeters per second to standard SI meters per second units:
$$v = \frac{3000}{100} = 30\ \text{m/s}$$
The time taken for the wave front to travel across the entire length of the string is $t = 0.5\ \text{seconds}$. Now compute the length $L$:
$$L = v \cdot t = 30 \times 0.5 = 15\ \text{m}$$
Step 4: Final Answer:
The total length of the string is $15\ \text{m}$, which corresponds to option (D).