PHYSICS

 Answer:  Inner pulleys are smaller than others to eradicate the frictional force between the ropes and inner pulleys while in use.

Spanner has a long handle. Why? Answer: When perpendicular distance between the force and the axis of rotation is large, smaller force is required to produce  the desired torque.

Terminal voltage of a dry cell is 1.3 V. It means that the cell can supply 1.3J of energy to move unit positive charge across its terminals in the external circuit connected to the cell.

Emf of a dry cell is 1.5 V. It means that the cell can supply 1.5 joule of energy to move 1 coulomb of charge all around the circuit ( outside and inside  the cell).

  MCB stands for  a) miniature circuit board  b) miniature circuit band c) miniature circuit breaker d) miniature circuit blocker Ans: c

Q1: What is radioactivity? A:  The  phenomenon of spontaneous emission of alpha particle or beta particle and gamma rays  from an unstable nucleus is called radioactivity.   Q2: When does a nucleus  become unstable ? A: When the number of neutrons become much more than that of protons. Q3: Which part of the atom takes part in radioactivity ? A: Nucleus Q4: What happens to the radioactive behaviour of a radioactive sample if it is chemically oxidized ? A: The radioactive behaviour does not change. As oxidation is the chemical change, it does not affect the nuclear activity. Q5: How does the atomic number and mass number change if a radioactive nucleus releases one alpha particle ? A: Atomic number decreases by 2 and mass number decreases by 4 Q6: How does the atomic number and mass number change if a radioactive nucleus releases one beta particle? A: Atomic number increases by 1 and mass number does not change.

Q. If a simple pendulum is taken to the moon from the earth without changing the length, what is the effect on it's time period? Ans: As the time period of a simple pendulum is inversely proportional to the square root of acceleration due to gravity and the acceleration due to gravity of the moon is less than that of the earth, time period increases (square root of 6 times)