Answer:
B. 
Explanation:
Assuming we are dealing with a perfect gas, we should use the perfect gas equation:
With T the temperature, V the volume, P the pressure, R the perfect gas constant and n the number of mol, we are going to use the subscripts i for the initial state when the gas has 20 cubic inches of volume and absolute pressure of 5 psi, and final state when the gas reaches 10 psi, so we have two equations:
(1)
(2)
Assuming the temperature and the number of moles remain constant (number of moles remain constant if we don't have a leak of gas) we should equate equations (1) and (2) because 
, 
and R is an universal constant:
, solving for 
Answer:
Length, l = 33.4 m
Explanation:
Given that,
Electrical field, 
Let the electrical potential is, 
We need to find the length of a thundercloud lightning bolt. The relation between electric field and the electric potential is given by :
So, the length of a thundercloud lightning bolt is 33.4 meters. Hence, this is the required solution.
<h2>The temperature of the air is 66.8° C</h2>
Explanation:
From the Newton's velocity of sound relationship , the velocity of sound is directly proportional to the square root of temperature .
In this case The velocity of sound = frequency x wavelength
= 798 x 0.48 = 383 m/sec
Suppose the temperature at this time = T K
Thus 383 ∝ 
I
The velocity of sound is 329 m/s at 273 K ( given )
Thus 329 ∝ 
II
Dividing I by II , we have
= 
or 
= 1.25
and T = 339.8 K = 66.8° C
I'm not sure about the rest but for question 2:
A theory is an attempt to come up with a big picture of all we know so far. It also drives future research as people do experiments to see if what the theory predicts actually happens. When experiments don’t support the theory, you have to change the theory and try again. That’s how science works. We come up with a “best guess” (theory), and then do research to test it’s accuracy. As we discover contradictions, we adjust the theory to take those into account, and then start testing the validity of the new theory.
Answer:
The mechanical advantage of the system is equal to 19.62
Explanation:
The ratio of the force produced by a machine to the force applied to it is called mechanical advantage. In other words it is the ratio of output force to the input force.
In this problem mass=200kg
applied force=100N
input force=100N
output force=
mechanical advantage 
It gives an idea about the efficiency of a mechanical device. It is indeed a measure of force amplification. In block and tackle system an assembly of ropes and pulleys is used to lift loads. When the moving block is supported by a greater number of rope sections the force amplification will be more.
