PART - 1 CH - 1 Units and Measurements — Physics STD 11 Science — Question

Explain why When we try to close a water tap with our fingers, fast jets of water gush through the openings between our fingers.

Write the order of following length in metres:

1. Radius of earth.
2. The height of average man.
3. Thickness of sheet of paper.
4. The radius of hydrogen atom.

Why are space rockets usually launched from west to east in the equatorial plane?

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)?

Moment of inertia of uniform circular disc about a diameter is I. What is the moment of inertia about an axis perpendicular to its plane and passing through a point on its rim?

Change in internal energy is independent of path followed. Is it true? Why?

Why are porcelain objects wrapped in paper or straw before packing for transportation?

A retarding force is applied to stop a motor car. If the speed of the motor car is doubled, how much more distance will it cover before stopping under the same retarding force?

Can a hydrogen atom emit characteristic X-rays?

Are all dimensionally correct equations numerically correct? Give one example.