The correct answer is the following.
The forces that act on the piano are: 2) gravitational force acting on the piano (piano's weight). 5) force of the floor on the piano (normal force). 7) force of Chadwick on the piano.
As we see in the picture that I have attached is Chadwick pushing the piano in a horizontal plane. So Chadwick is applying a force that produces an acceleration. It is his force on the piano plus the acceleration of the weight of the piano, it's a gravitational force. This is pure physics applied to an object.
The wavelength of the first harmonic of the standing wave is 2L.
<h3>What is a standing wave?</h3>
A standing wave is one in which the obvious points remain fixed as the vibration continues. A standing wave occurs in a wind instrument such as a trumpet, saxophone etc.
We know from the formula of the first harmonic that the wavelength of the first harmonic of the standing wave is 2L.
Learn more about standing wave:brainly.com/question/1121886?
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<span>Scientists have obtained most of this information from natural geological activity.
</span>S-waves and p-waves are seismic waves- the waves of energy that travel through the Earth as a result of an earthquake .Both P- and S-waves travel easily through solids, but S-waves cannot pass through liquids, and they cannot pass through the outer core. Scientists know that Earth’s outer core is liquid because s-waves are not able to pass through it.<span> When an earthquake occurs there is a “shadow zone” on the opposite side of the earth where no s-waves arrive.
</span>So, one of the reasons <span>why scientists believe the outer core is liquid is the s-wave shadow zone.</span>
