Important Examination Questions and Solutions (Physics)

Q1. Very Short Answer Questions:

a) Do dimensionally correct relations necessarily be correct? Justify.

Ans:  An equation for a physical relation must be dimensionally correct to be valid. However, a dimensionally correct equation is not necessarily correct physically. An equation can be dimensionally correct, but the dimension not refer to any physical quantity.

b) What do you mean by resolution vector? Give examples.

Ans:  any vector directed at an angle to the horizontal (or the vertical) can be thought of as having two parts (or components). ... For example, if a chain pulls upward at an angle on the collar of a dog, then there is a tension force directed in two dimensions.

c) A bucket containing water is rotated in a vertical circle. Why does not water fall?

Ans:  For its revolution in a vertical circle,water [n the bucket needs a centripetal force. The weight of the water due to which water can fall is used up in providing the necessary centripetal force and the water does not fall.

d) Which one is more elastic, rubber or steel ?

Ans: Steel is more elastic than rubber because steel comes back to its original shape faster than rubber when the deforming forces are removed.Elasticity In Physics And In Common Life: In common life we label a substance as more elastic if it can be stretched more than others.

e) Tiny insects walk on the surfaces of water at rest, explain why?

Ans: The surface of any body of water behaves as though it is covered with an invisible skin, which allows small, light-weight insects to walk across it. This skin effect is caused by surface tension. Like molecules are attracted to each other. They like to “stick together” and this attractive force is known as cohesion.

f) Differentiate between elasticity and plasticity.

Ans: Elasticity is the ability of an object or material to resume its normal shape after being stretched or compressed. Hence,elasticity is a physical property. Materials showing a high degree of elasticity are termed elastic materials.

e) Write short note about absolute zero temperature.

Ans: At the physically impossible-to-reach temperature of zero kelvin, or minus 459.67 degrees Fahrenheit (minus 273.15 degrees Celsius), atoms would stop moving. As such, nothing can be colder than absolute zero on the Kelvin scale.

f) Why star twinkle?

Ans: Stars do not really twinkle, they just appear to twinkle when seen from the surface of Earth. The stars twinkle in the night sky because of the effects of our atmosphere. When starlight enters our atmosphere it is affected by winds in the atmosphere and by areas with different temperatures and densities.

e) Is Makeup mirror concave or convex ?

Ans: For example, the passenger-side rear view mirror on a car is convex. You may have noticed that many of these mirrors say "Objects in mirror are closer than they appear." This is because the objects are made smaller by the mirror, so they appear farther away! ... Makeup mirrors and dental mirrors are concave mirrors.

f) What is electrostatic shielding?

Ans: Electrostatic shielding is the phenomenon that is observed when a Faraday cage operates to block the effects of anelectric field. Such a cage can block the effects of an external field on its internal contents, or the effects of an internal field on the outside environment.

g) Can a charged body attract an uncharged body? Explain.

Ans: Yes, Charged particles indeed attract uncharged ones. The negatively charged body can be thought to be an electron rich specie. When brought near the uncharged body, it repels the free electrons from the uncharged body towards its farther end.

h) Why is a baby wrapped tightly with warm cloth than an adult in winter?

Ans: We dress and cover them very well. When they sleep, they don't move and therefore they don't produce extra heat. So the warm wrapping is important.

Q2. Short Answer Questions.

1) State parallelogram law of vector addition and find its resultant, both magnitude

and direction.

2) What is relative velocity? Discuss the method of determination of relative velocity and direction

3) Differentiate between surface tension and surface energy of liquid. Establish the relation.

4) Define Young 's modulus of elasticity. Describe how you can determine it experimentally.

5) Define the terms coefficients of real and apparent expansion of liquid and establish their relation.

6) State Newton's law of cooling. Explain the theory for determine the specific heat capacity of liquid by method of cooling.

7) Define focal length of concave mirror and establish its mirror formula.

8) Define angle of prism. Show that deviation produced by small angle prism is independent with angle of incidence.

9) State Coulomb's law. Find the expression for electrostatic force between two charges in dielectric medium.