The correct answer to the question is C i.e C represents the friction from air resistance.
EXPLANATION:
Before coming into any conclusion, first we have to understand friction.
The friction is the opposing force which acts tangentially between two bodies in contact when there is a relative motion between them.
The air resistance is that frictional force which is provided by the air to the moving body through it. Hence, the friction from air resistance will be directed opposite to the motion of the body.
In the given diagram, the airplane is going horizontally. The force A acts in forward direction while force C acts in backward direction. The forces B and D are acting vertically. There is no motion in vertical direction. Hence, the net force of A and C will cause the airplane to move.
As the plane is moving along the direction of A, the frictional force must act along the direction of C.
Answer:
The mass is 
Explanation:
From the question we are told that
The initial temperature is 
The final temperature is 
Generally the maximum heat produced by 1 Liter of natural gas is
So the amount of heat produced by 100 L is

=> 
Generally given that the efficiency is 
Then actual heat received by the water is

=> 
=>
Converting to kcal
=> 
Generally the specific heat of water is

Generally the heat received by the water is mathematically represented as

=> 
=> 
<span>2.56 sec (t=1/0.39)
f=3.9/10</span>
Answer:

Explanation:
As we know by the law of diffraction through circular aperture

here we know that
a = diameter of the aperture
= diffraction angle
= wavelength
now we have

Now in order to find the wavelength we know



now we have



The answer is: [C]: "protons and electrons" .
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