Physics, 08.03.2021 20:10 ryliekarenbowers

If Tom were so foolish as to play his keyboard instrument under water, where the speed of sound is 1500 m/s , what would be the wavelength of the B note in water ? Explain why the B tone has a longer wavelength in water than in air. (frequency of middle B tone is 494 Hz )

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Answer from: clashofclans17

λ = 3.04 m

Explanation:

At any traveling wave, there exists a fixed relationship between speed, wavelength and frequency, as follows:

$v = \lambda* f (1)$

We know the value of speed of sound in water (1500 m/s), and the frequency of middle B tone (494 Hz) , so we can find the wavelength λ (in meters) as follows:

$\lambda_{w} = \frac{v_{sw}}{f} = \frac{1500m/s}{4941/s} = 3.04 m (2)$

Since the frequency is the same at any medium, and the speed of sound in air is lower than in water (334 m/s) this means that the wavelength in water must be longer than in air.

Answer from: Quest

Where are the options ?

Answer from: Quest

force is based upon mass and acceleration.the statement is not always true.

it can be explained from newton's second law of motion.

as per newton's second law of motion the rate of change of momentum is directly proportional to the applied force and takes place along the direction of force.

mathematically it can be written as -

$f\alpha \frac{dp}{dt}$

⇒ $f= k \frac{dp}{dt}$

here k is the proportionality constant whose value is 1.

$f=\frac{dp}{dt}$

$f= \frac{d[mv]}{dt}$

$f= m\frac{dv}{dt} +v\frac{dm}{dt}$

$f=ma+v\frac{dm}{dt}$ [a is the acceleration=dv/dt]

hence we see that force not only depends on mass and acceleration but also on velocity and rate of change of mass. force f will depend on mass and acceleration only when mass is constant.

hence the statement that force is based upon mass and acceleration is false.