What is the principle used in common balance?

What is the principle used in atom bomb?

What is the principle behind a beam balance?

What is the principle used in wheel and axle? Mention its applications.

What is the principle used in photocell? State any two applications of photocell.

Write the principle used in beam balance and define Mechanical Advantage.

a. What is the principle used in optical fibres ? b. Explain briefly the working principle. c. What are the uses of optical fibres ?