A black hole is a cosmological object that is created when a massive star comes to the end of its life and collapses under its own gravity. Black holes have massive gravitational fields that even light cannot escape beyond a certain distance. Before being engulfed, matter that is pulled into a black hole should become very hot and emit electromagnetic radiation.
Explanation:
Average speed = distance / time
|v| = (7 km + 2 km) / (2 hr + 1 hr)
|v| = 3 km/hr
Average velocity = displacement / time
v = (7 km east + 2 km east) / (2 hr + 1 hr)
v = 3 km/hr east
Answer:
Explanation:
Point beneath you forms a beautiful iridescent green
refractive index of Gasoline 
Wavelength of Green light is 
Here light first traverse from air(n=1) to gasoline , it reflects from front surface of gasoline(n=1.38) so it suffers a phase change. After this light reflect from rear surface of gasoline and there is a decrease in refractive index(n=1.38 to n=1.33), so there is no phase change occurs .
For constructive interference
here t= thickness of gasoline film
n=refractive index
for 
The only function of the pulleys in the diagram is to change the direction
of the force applied to raise the bricks.
<h3>What is a Pulley?</h3>
A pulley is a wheel which has a flexible rope on its rim and helps to
transmit energy and motion.
In the diagram given, we can see that the pulley is used to raise a mass of
block by three people. They pull the rope horizontally in order to raise the
block vertically. This means that it was used to change the direction of the
applied force.
Read more about Pulley here brainly.com/question/177456
