Answer:
b) Betelgeuse would be  times brighter than Sirius
 times brighter than Sirius
c) Since Betelgeuse brightness from Earth compared to the Sun is  the statement saying that it would be like a second Sun is incorrect
 the statement saying that it would be like a second Sun is incorrect
Explanation:
The start brightness is related to it luminosity thought the following equation:
 (1)
 (1)
where  is the brightness,
 is the brightness,  is the star luminosity and
 is the star luminosity and  , the distance from the star to the point where the brightness is calculated (measured). Thus:
, the distance from the star to the point where the brightness is calculated (measured). Thus:
b)  and
 and  where
 where  is the Sun luminosity (
 is the Sun luminosity ( ) but we don't need to know this value for solving the problem.
) but we don't need to know this value for solving the problem.  is light years.
 is light years.
Finding the ratio between the two brightness we get:

c) we can do the same as in b) but we need to know the distance from the Sun to the Earth, which is  . Then
. Then

Notice that since the star luminosities are given with respect to the Sun luminosity we don't need to use any value a simple states the Sun luminosity as the unit, i.e 1. From this result, it is clear that when Betelgeuse explodes it won't be like having a second Sun, it brightness will be 5 orders of magnitude smaller that our Sun brightness. 
 
        
             
        
        
        
1 point energy should be the answer
        
             
        
        
        
Answer:
Explanation:
a) Energy stored in spring = 1/2 k x² = .5 x k 0.1² 
500 = 5 x 10⁻³ k , 
k = (500/5) x 10³ = 10⁵ N/m 
b )
k = 4.5 x 10¹ = 45 N/m
Stored energy = 1/2 k x² = .5 x 45 x 8² x 10⁻⁴ =1440 x 10⁻⁴ J
This energy gets dissipated by friction .
work done by friction = μ mg d 
d is the distance traveled under friction
so 1440 x 10⁻⁴ = μ x 3 x 9.8 x 2
μ = 245 x 10⁻⁴  or 0.00245 which appears to be very small. .
 
        
             
        
        
        
Temperature doesn't really affect solubility on liquids so it can only be D besides it's already a liquid....