Explanation:
Given that,
The mass of rock, m = 2.35-kg
It was released from rest at a height of 21.4 m.
(a) The kinetic energy is given by : 
As the rock was at rest initially, it means, its kinetic energy is equal to 0.
(b) The gravitational potential energy is given by : 
It can be calculated as :

(c) The mechanical energy is equal to the sum of kinetic and potential energy such that,
M = 0 J + 492.84 J
M = 492.84 J
Hence, this is the required solution.
Answer:
Approximate escape speed = 45.3 km/s
Explanation:
Escape speed

Here we have
Gravitational constant = G = 6.67 × 10⁻¹¹ m³ kg⁻¹ s⁻²
R = 1 AU = 1.496 × 10¹¹ m
M = 2.3 × 10³⁰ kg
Substituting

Approximate escape speed = 45.3 km/s
Answer:
708.3 Hz
Explanation:
For an open-air column, like the empty can, the fundamental frequency is given by

where
v = 340 m/s is the speed of sound
L is the length of the column
In this problem, the length of the bottle is
L = 24 cm = 0.24 m
Therefore, the fundamental frequency is

Ultrasound is vibrations, just like sound is vibrations. Ultrasound travels though the body just like sound would and when it hits something, it bounces back, where it is picked up by a receiver. which then makes an image out of it.
X-rays are electromagnetic waves, like visible light. Other examples of electromagnetic waves are infrared, and ultraviolet. But people cant see infrared nor ultraviolet, even though they are just like visible light. The difference between visible light and all these other kinds of light are just like the difference between red and blue. They are both light but different colors, ultraviolet and infrared are colors we cannot see, and in fact, we can see only a tiny portion of the colors out there. X-rays are just like all these kinds of light and we cant see it but it is able to go through most of the body, bot not bone. Doctors use x-rays to see bones and things like that in the body because x-rays won't pass through bone, but they will go through muscle and skin. So when a doctor takes an x-ray, its just like making a silhouette, but with colors we cant see. Of course, the x-rays make the photo paper change color and that's how we are able to see the image but the principle is the same.
Answer:
★The second law of refraction
The ratio of sine of angle of incidence to the sine of angle of refraction is a constant for a light of given colour and for a given pair of media. This law is also called Snell's law of refraction. If 'i' is the angle of incidence and 'r' is the angle of refraction then, Sin i/Sin r = constant
This constant value is called the refractive index of the second medium with respect to the first.