Grinding pepper is a physical change
Answer:

Explanation:
From the question we are told that
Distance b/e antenna's 
Frequency of antenna Radiation
Distance from receiver 
Intensity of Receiver 
Distance difference of the receiver b/w antenna's 
Generally the equation for Phase difference
is mathematically given by



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Therefore phase difference f between the two radio waves produced by this path difference is given as

Some examples of when friction is helpful are: to help the movement of tires. When you walk, and also, when you erase. :)
Displacement will be 15 too because
It falls from 0 till 15 meters
Answer:
Explanation:
a ) Earlier emf of cell applied on R₁ but now emf will be distributed among R₁ and R₂
Potential difference on R₁ will become less .
b ) Current is inversely proportional to resistance of the circuit. As resistance increases , current will be less . So current through R₁ will become less.
c )
When resistance is added in series , they are added up to obtain equivalent resistance . So equivalent resistance R₁₂ will be more than R₁ OR R₂.