Work, Energy, and Power — Physics STD 11 Science — Question

A ladder is learning against a wall. If it slips, where will its instantaneous center of rotation be?

What forbids the complete conversion of heat into work?

A stone breaks the window glass into pieces, while a bullet pierces through the same. Why?

Two astronauts on the surface of moon cannot talk to each other. Why?

Answer the following :
The triple-point of water is a standard fixed point in modern thermometry. Why? What is wrong in taking the melting point of ice and the boiling point of water as standard fixed points (as was originally done in the Celsius scale)?

For any given metal the Young's Modulus of elasticity is 2.4 times the modulus of rigidity. What would be its poisson ratio?

A spring is stretched. Is the work done by the stretching force positive or negative?

If oil of density higher than density of water is used in a resonance tube, how will the frequency change?

Which of the following examples represent periodic motion?
A freely suspended bar magnet displaced from its N-S direction and released.

What type of energy stored in:

1. The wound spring of a watch.
2. A stretched bow while ready to project an arrow?