Assertion:  Liquid molecules have greater potential energy at the melting point.

Reason:  Intermolecular spacing between molecules increases at melting point.

• If both assertion and reason are true and reason is the correct explanation of assertion.

• If both assertion and reason are true but reason is not the correct explanation of assertion.

• If assertion is true but reason is false.

• If both assertion and reason are false.

Assertion: A needle placed carefully on the surface of water may float, whereas a ball of the same material will always sink.

Result: The buoyancy of an object depends both on the material and shape of the object.

• If both assertion and reason are true and reason is the correct explanation of assertion

• If both assertion and reason are true but reason is not the correct explanation of assertion

• If assertion is true but reason is false

• If both assertion and reason are false

In old age arteries carrying blood in the human body become narrow resulting in an increase in the blood pressure. This follows from

• Pascal's law

• Stoke's law

• Bernoulli's principle

• Archimede's principle

Which of the following physical quantities do not have same dimensions?

• pressure and stress

• tension and surface tension

• strain and angle

• energy and work

Work of 3.0 × 10^-4 joule is required to be done in increasing the size of a soap film from 10 cm ×  6 cm to 10 cm ×  11 cm. The surface tension of the film is

• 5 ×  10^-2 N/m

• 3 ×  10^-2 N/m

• 1.5 ×  10^-2 N/m

• 1.2 ×  10^-2 N/m

If the water falls from a dam into a turbine wheel 19.6 n below, then the velocity of water ar turbines  is ( Take g = 9.8 m/s )

• 9.8 m/s

• 19.6 m/s

• 39.2 m/s

• 98.6 m/s

Assertion: Machine parts are jammed in winter. 

Reason:  The viscosity of lubricant used in machine parts increase at low temperatures.

• If both assertion and reason are true and reason is the correct explanation of assertion

• If both assertion and reason are true but reason is not the correct explanation of assertion

• If assertion is true but reason is false

• If both assertion and reason are false

Assertion: Use of ball bearings between two moving parts of a machine is a common practice. 

Reason:  Ball bearings reduce vibrations and provide good stability.

• If both assertion and reason are true and reason is the correct explanation of the assertion

• If both assertion and reason are true but reason is not the correct explanation of the assertion

• If assertion is true, but reason is false

• Both assertion and reason are false statements

139.

Assertion: A thin stainless steel needle can lay floating on a still water surface. 

Reason:  Any object floats when the buoyancy force balances the weight of the object.

• If both assertion and reason are true and reason is the correct explanation of the assertion

• If both assertion and reason are true but reason is not the correct explanation of the assertion

• If assertion is true, but reason is false

• Both assertion and reason are false statements

A candle of diameter d is floating on a liquid in a cylindrical container of diameter D ( D >> d ) as shown in figure. If it is burning at the rate of 2 cm/hour then the top of the candle will

• remain at the same height

• fall at the rate of 1 cm/hour

• fall at the rate of 2 cm/hour

• go up at the rate of 1 cm/hour