# University physics, waves, multiple choice.

• thinktoohard
In summary, to find the length of a cord with a mass of 40g and a tension of 19.2N, with a natural frequency of 10Hz, the equation L = v/(2f) can be used, where v = √(FT/(m/(v/2f))) and L is the length of the cord, v is the velocity, f is the frequency, FT is the force tension, and m is the mass. This results in a length of 1.2125 meters and a time of 0.05 seconds for the wave to travel from one end of the string to the other.
thinktoohard

## Homework Statement

A cord with a mass of 40g is tied between two supports with a tension of 19.2N. The natural frequency of the cord is 10Hz. Find the length of the cord

a.1.2m b.2m c.289m d.34cm

Using your answer from Question 3, how long does the wave take to travel from one end of the string to the other?

a.0.1s b.0.05s c.50s d.20s

## Homework Equations

v=squrt(forcetension/(mass/length))
v=wavelength/Period=wavelength*frequency

## The Attempt at a Solution

Knowns:
fixed ends, string.
mass = 0.040 kg
Force Tension = 19.2N
Natural Frequency = 10Hz
length of the cord = ?

Calculated:
Period = 0.1 s
Weight = 0.392 N

Other stuff:
Velocity = ?
Wavelength = 2L = ?

I've basically just stared at it and played around with everything I can think of which gets me no where close to an answer, for the past hour trying to figure out what to do, Made an account just to ask this forum about it.

Last edited:
Hello, thinktoohard. Welcome to PF!

You need to show some attempt at a solution to receive help here.

You've got two "relevant equations" and one "other stuff equation" λ = 2L.

Show us your attempt at combining those equations to get a single equation for L in terms of the given quantities.

Thanks anyways I figured it out, Sub λ = 2L -> f = v/λ -> L = v/(2f), -> sub into v = sqrt.(ft/(m/L)) for -> v = sqrt.(FT/(m/(v/2f))) then isolate for v, gives you v = 24.25 m/s, -> v/2f = L -> L = 1.2125 -> L/v = 0.05 s.

## 1. What is the difference between longitudinal and transverse waves?

Longitudinal waves are waves in which the particles of the medium vibrate parallel to the direction of wave propagation, while transverse waves are waves in which the particles of the medium vibrate perpendicular to the direction of wave propagation. In other words, longitudinal waves have compressions and rarefactions, while transverse waves have crests and troughs.

## 2. How are frequency and wavelength related in a wave?

Frequency and wavelength are inversely proportional in a wave. This means that as frequency increases, wavelength decreases, and vice versa. This relationship is described by the equation λ = v/f, where λ is wavelength, v is wave speed, and f is frequency.

## 3. What is the difference between constructive and destructive interference?

Constructive interference occurs when two waves of the same frequency and amplitude meet and combine to produce a wave with a larger amplitude. Destructive interference, on the other hand, occurs when two waves of the same frequency and amplitude meet and cancel each other out, resulting in a wave with a smaller amplitude.

## 4. How does the speed of a wave change when it travels from one medium to another?

The speed of a wave changes when it travels from one medium to another. This is because the speed of a wave is dependent on the properties of the medium it is traveling through, such as density and elasticity. When a wave travels from a less dense medium to a more dense medium, its speed decreases, and when it travels from a more dense medium to a less dense medium, its speed increases.

## 5. What is the difference between a standing wave and a traveling wave?

A standing wave is a wave that appears to be standing still, as it is formed by the interference of two waves traveling in opposite directions. It has nodes, where the amplitude is always zero, and antinodes, where the amplitude is always maximum. A traveling wave, on the other hand, is a wave that is constantly moving forward and carries energy from one point to another.

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