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

Place a safety pin on a sheet of paper. Hold the sheet over a burning candle, until the paper becomes yellow and charr. On removing the pin, its white trace is observed on the paper. Why?

The two ends of a spring balance are pulled each by a force of 10kg wt. What will be the reading of the balance?

Can the direction of velocity change while keeping the value of acceleration constant?

An experimenter measures the length of a rod. Initially the experimenter and the rod are at rest with respect to the lab. Consider the following statements:

1. If the rod starts moving parallel to its length but the observer stays at rest, the measured length will be reduced.
2. If the rod stays at rest but the observer starts moving parallel to the measured length of the rod, the length will be reduced.

Should the value of escape velocity be less or more on the surface of Moon as compared to Earth?

A source emits 45 joules of energy in 15s. What is the radiant flux of the source?

On what factors does the critical speed of fluid flow depend?

If all the objects radiate electromagnetic energy, why do not the objects around us in everyday life become colder and colder?

The velocity of a particle is towards west at an instant. Its acceleration is not towards west, not towards east, not towards north and not towards south. Give an example of this type of motion.