Physics Questions & Answers - Free Online Practice

3,766.

Heat is radiated by hot objects in the form?

x-rays

light energy

infrared rays

solar energy

Correct answer is C

Infrared rays falling on the skin causes the skin causes the sensation of warmth. since the objects are hot, the correct option is informed.

3,767.

The density of a certain oil on frying becomes 0.4 kgm\(^{-3}\) with the volume of 20m\(^{3}\). what will be its initial volume when its initial density is 0.8 kgm\(^{-3}\) assuming no loss of oil due to spillage?

12m³

10m³

8m³

5m³

View answer & explanation

Correct answer is B

Density (D) = \(\frac{mass}{volume}\)

\(\therefore Mass = Density \times volume\)

= \(0.4 \times 20 = 8kg\)

The initial volume = \(\frac{Mass}{\text{Initial density}}\)

= \(\frac{8}{0.8} = 10m^{3}\)

3,768.

One special advantage of alcohol over mercury as a thermometric liquid is its?

low density

low freezing point

high specific

low boiling point

View answer & explanation

Correct answer is B

The low freezing point of alcohol, -115°c enable low temperatures to be measured. mercury freezes at 39°c, and cannot be used in countries like Russia where winter temperatures of -40°c are common

3,769.

A hydrometer is an instrument used in measuring?

vapour pressure of a fluid

density of liquid

relative humidity of a liquid

relative density of a liquid

View answer & explanation

Correct answer is D

The instrument used in measuring relative density is hydrometer

3,770.

The accurate measurement of the relative density of a substance in its powdered form is done with a beam balance and?

a density bottle

an eureka can

a pipette

a burette

View answer & explanation

Correct answer is A

Since relative density = mass of substance
mass of equal volume of water relative density bottle should be used to determine the mass of the substance, and mass of an equal volume of water by filling the bottle with the powder and water respectively and weighed with the beam balance.