Answer:
laws of motion relate an object’s motion to the forces acting on it. In the first law, an object will not change its motion unless a force acts on it. In the second law, the force on an object is equal to its mass times its acceleration. In the third law, when two objects interact, they apply forces to each other of equal magnitude and opposite direction.
This question involves the concepts of echo, ultrasonic images, ultrasonic sound waves.
The process of ultrasonic images uses the "echo" property of the sound waves.
Echo is the property of the sound wave by the virtue of which the sound wave reflects back to the source of the sound after hitting a surface or an object.
Ultrasonic images are obtained from inside organs of our body. This process involves the use of ultrasonic sound waves that have a frequency greater than 20,000 Hz. These sound waves are out of the range of audible sound by the human ear. When these ultrasonic sound waves are sent in form of pulses into the human body by the use of probes, they reflect back from the tissues of different organs to the probe. The probe then records the reflection properties of these sound waves and displays them in form of an image, known as ultrasonic images.
Learn more about echo here:
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The attached picture shows the process of ultrasonic imaging.
Answer:
20 hertz of frequency produced.
Explanation:

Here we will find frequency and period should be in second, here given: 0.05 seconds
using the formula:


Because dark line spectra result from passing white light through ionized gasses and plasmas, which is what the atmosphere of stars are made of. These frequencies are scattered by the star's atmosphere as it leaves the surface (photosphere) of the star, and don't make it to earth.
Answer:
8.89288275 m/s
Explanation:
F = Tension = 54 N
= Linear density of string = 5.2 g/m
A = Amplitude = 2.5 cm
Wave velocity is given by

Frequency is given by

Angular frequency is given by

Maximum velocity of a particle is given by

The maximum velocity of a particle on the string is 8.89288275 m/s