1answer.
Ask question
Login Signup
Ask question
All categories
  • English
  • Mathematics
  • Social Studies
  • Business
  • History
  • Health
  • Geography
  • Biology
  • Physics
  • Chemistry
  • Computers and Technology
  • Arts
  • World Languages
  • Spanish
  • French
  • German
  • Advanced Placement (AP)
  • SAT
  • Medicine
  • Law
  • Engineering
Marat540 [252]
2 years ago
6

What do astronomers mean by light pollution?

Physics
1 answer:
Komok [63]2 years ago
7 0
Light pollution is influence of the light on earth (for example, street lighting) which interrupt observations. For example, if you are in a street during the night and street lights are turned on you won't see stars, but if lighting is turned off or if you go out of town you will see stars above.
You might be interested in
A record is dropped vertically onto a freely rotating (undriven) turntable. Frictional forces act to bring the record and turnta
alexgriva [62]

Answer:

The loss of initial Kinetic energy = 37.88 %

Explanation:

Given:

Rotational inertia of the turntable = I_t

Rotational inertia (I_r) of the record = 0.61\times I_t

According to the question:

<em>Frictional forces act to bring the record and turntable to a common angular speed.</em>

So,angular momentum will be conserved as it is an inelastic collision.

Considering the initial and final angular velocity of the turn table as  \omega _i\  ,\  \omega_f respectively.

Note :

Angular momentum (L) = Product of moment of inertia  (I)  and angular velocity (\omega) .  

Lets say,

⇒ initial angular momentum = final angular momentum

⇒  L_i=L_f

⇒ (I_t)\times \omega_i = (I_t+I_r)\times \omega_f

⇒ \omega _f=\frac{I_t}{I_t+I_r} \times (\omega_i) ...equation (i)

Now we will find the ratio of the Kinetic energies.

⇒ K_i=\frac{I_t\times \omega_i^2}{2}       ⇒ K_f=\frac{(I_r+I_t)\times \omega_f^2}{2}

Their ratios:

⇒ \frac{K_f}{K_i} =\frac{\frac{(I_t+I_r)\times \omega_f^2}{2} }{\frac{I_t\times \omega_i^2}{2} }    

⇒ \frac{K_f}{K_i} = {\frac{(I_t+I_r)\times \omega_f^2}{2} } \times {\frac{2}{I_t\times \omega_i^2}}

Plugging the values of  \omega _f^2 as \omega _f^2 =(\frac{I_t}{I_t+I_r} \times \omega_i\ )^2 from equation (i) in the ratios of the Kinetic energies.

⇒ \frac{K_f}{K_i} =\frac{(I_t+I_r)\times \frac{(I_t)^2}{(I_t+I_r)^2} \times \omega_i^2}{I_t\times \omega_i^2} =\frac{(I_t)^2}{(I_t+I_r)}\times \frac{1}{I_t}=\frac{I_t}{I_t+I_r}

Now,

The Kinetic energy lost in fraction can be written as:

⇒ \frac{K_f-K_i}{K_i}

Now re-arranging the terms.

\frac{K_f-K_i}{K_i}  =(\frac{K_f}{K_i} -1)= \frac{I_t}{I_t+I_r} -1=\frac{I_t-I_t-I_r}{I_t+I_r} =\frac{-I_r}{(I_t+I_r)}

Plugging the values of  I_r and I_t .

⇒ \frac{K_f}{K_i} = \frac{-0.61I_t}{0.61I_t+I_t} =\frac{-0.61}{1.61} =-0.3788

To find the percentage we have to multiply it with 100 and here negative means for loss of Kinetic energy.

⇒ \frac{K_f}{K_i} = =-0.3788\times 100= 37.88

So the percentage of the initial Kinetic energy lost is 37.88

4 0
2 years ago
What is the time lapse between seeing a lightning strike and hearing the thunder if the lightning flash is 47 km away? The speed
Natali5045456 [20]

Answer:

141.14098 secs

Explanation:

Time taken to see the lightning flash can be gotten from:

Velocity = distance/time

Time = distance/velocity

Time = (47 * 1000)/(3 * 10^8)

Time = 0.0001567 secs

Time taken to hear the thunder can be gotten from:

Velocity = distance/time

Time = distance/velocity

Time = (47 * 1000)/(333)

Time = 141.14114 secs

The time lapse between the lightning flash and the thunder will be:

141.14114 - 0. 0001567

= 141.14098 secs

6 0
3 years ago
How do the valves do in the heart​
Rina8888 [55]

Answer:

The valves prevent the backward flow of blood. These valves are actual flaps that are located on each end of the two ventricles (lower chambers of the heart). They act as one-way inlets of blood on one side of a ventricle and one-way outlets of blood on the other side of a ventricle.

Explanation:

8 0
3 years ago
Answer this question ASAP please and thank you
allochka39001 [22]
The answer is Oscar Robertson and Jerry West !! hope this helps :p
8 0
3 years ago
Read 2 more answers
Among the alkali earth metals, the tendency to react with other substances
padilas [110]
Answer D
In alkali earth metals reacrivity increases from top to bottom (opposite of b)
This is because as you go down, the electron shells increase by 1 shell. The farther away a shell is from the nucleus, the higher its tendency to react.
D is true because the more reactive an alkali metal is, the more vigorous the reaction will be with water.
4 0
2 years ago
Read 2 more answers
Other questions:
  • a ball is thrown horizontally from a 20 m high building with a speed of 5.0 m/s. How far from the base of the building does the
    5·1 answer
  • Can Someone help me answer the question?
    14·1 answer
  • How do exons and introns differ?
    8·1 answer
  • In order to move a bag of dog food across a 10 meter room you apply20 Newton’s of force how much work was done?
    15·1 answer
  • All the bats living in a cave form a _______ of bats in the cave ecosystem.
    12·1 answer
  • Keaton is asked to solve the following physics problem:
    6·1 answer
  • Heat is transferred in three ways from one place to another. The mechanism of heat transfer whereby atoms or molecules of matter
    12·1 answer
  • In the nucleus of an atom, two protons are separated by a distance of 10^-13 m. What is the Coloumb force between them? The char
    13·1 answer
  • When a narrow laser beam passes through a fine wire mesh before arriving at the wall, it forms a complicated pattern of bright s
    7·1 answer
  • For this situation, i push on a heavy chair. suppose i push moderately on the chair, and this time the chair does move. then the
    11·1 answer
Add answer
Login
Not registered? Fast signup
Signup
Login Signup
Ask question!