Question

1.Why are Manhole covers Round?
2.If you look at a clock at the time is 3:15,What is the angle between the Hour and the minute Hands?
3.Why is there a matter to Antimatter Asymmetry?
4.What is Dark Matter?

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Answer 1

Answer:

1. Manhole covers are round because manholes are round. Manholes are round because it is the best shape to resist the compression of Earth around it.
2. Every 1 hr the hour hand moves 30 degrees and for minute hand moves 90 degrees in every 15 mins. Counting from 12:00 o'clock, at 3:15 the minute hand would be at 90 degrees and the hour hand would be at 3×30 +30/4 = 97.5 (Note- 1hr is divided into four 15mins.). So at 3:15 the Difference in angle is 97.5 - 90 = 7.5°
3. To understand why, let’s go back in time some 13.8 billion years to the Big Bang. This event produced equal amounts of the matter you are made of and something called antimatter. It is believed that every particle has an antimatter companion that is virtually identical to itself, but with the opposite charge. When a particle and its antiparticle meet, they annihilate each other—disappearing in a burst of light.
4. Dark matter is composed of particles that do not absorb, reflect, or emit light, so they cannot be detected by observing electromagnetic radiation. Dark matter is material that cannot be seen directly. We know that dark matter exists because of the effect it has on objects that we can observe directly.

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Answer 2

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1) Though this questions seems to stu.pid first, but has a very logical answer.

Here are some of the reasons:

• A round manhole cover cannot fall through its circular opening, whereas a square manhole cover could fall in if it were inserted diagonally in the hole.
• A round manhole cover is easily moved and rolled.
• Human beings have a roughly circular cross-section.

There could be many other reasons as well but I could think of these only.

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2) There is a formula to calculate it.

To calculate angle between hour and minute hand of a clock at any time m:n, where m us the hour and n is the minutes, is give by [60m - 11n]/2.

Here, the time is 3:15, so m =3 and n = 15

Thus, angle = [60(3) - 11(15)]/2 = 7.5°

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3) Thats such a nice question you put up! The answer too is very interesting.

Here you go,

The Big Bang should have created equal amounts of matter and antimatter in the early universe. But today, everything we see from the smallest life forms on Earth to the largest stellar objects is made almost entirely of matter. Comparatively, there is not much antimatter to be found. Something must have happened to tip the balance. One of the greatest challenges in physics is to figure out what happened to the antimatter, or why we see an asymmetry between matter and antimatter.

Antimatter particles share the same mass as their matter counterparts, but qualities such as electric charge are opposite.

Matter and antimatter particles are always produced as a pair and, if they come in contact, annihilate one another, leaving behind pure energy.

If matter and antimatter are created and destroyed together, it seems the universe should contain nothing but leftover energy.

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4) Another very interesting question.

Here is the answer:

Dark matter is a hypothetical invisible mass thought to be responsible for adding gravity to galaxies and other bodies.

Since the amount of visible material in galaxies can't account for their shapes, distributions, and movements, astrophysicists argue there must be a form of mass yet to be discovered. This mass doesn't appear to affect normal matter significantly in any other way - such as by absorbing or emitting photons - making it completely 'dark'.

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