Physics Questions

Q:

Ball bearings are used in cycles, scooters etc to

A) Increase the friction between the wheel and the axle B) Reduce the friction between the wheel and the axle
C) Reduce the friction between ground and the whee D) None of the above
 
Answer & Explanation Answer: B) Reduce the friction between the wheel and the axle

Explanation:
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Q:

It is difficult to fix a nail on a freely suspended wooden frame. Which law supports this statement?

 

A) Law of inertia B) Newton's second law
C) Newton's third law D) Pascal's law
 
Answer & Explanation Answer: C) Newton's third law

Explanation:
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Q:

The core of an electromagnet is made of soft iron because soft iron has 

A) small susceptibility and small retentivity B) large susceptibility and small retentivity
C) large density and large retentivity D) small density and large retentivity
 
Answer & Explanation Answer: B) large susceptibility and small retentivity

Explanation:
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Q:

Masses of stars and galaxies are usually expressed in terms of

A) neutron mass B) earth's mass
C) solar mass D) lunar mass
 
Answer & Explanation Answer: C) solar mass

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Q:

The working of the quartz crystal in the watch is based on the

A) Piezo - electric Effect B) Edison Effect
C) Photoelectric Effect D) Johnson Effect
 
Answer & Explanation Answer: A) Piezo - electric Effect

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Q:

The base of an electric iron is brightly polished mainly

A) to make it smooth and frictionless B) to make it rust-proof
C) to reduce heat loss by radiation D) to make it more durable
 
Answer & Explanation Answer: C) to reduce heat loss by radiation

Explanation:

Polished surfaces are poor radiators of heat. So loss of heat on that account is reduced and the electric iron remains hotter than otherwise.

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Q:

Consider the following statements :

1. There is no net moment on a body which is in equilibrium.

2. The momentum of a body is always conserved.

3. The kinetic energy of an object is always conserved.

Which of the statements given above is/are correct?

A) 1, 2 and 3 B) 2 and 3 only
C) 1 and 2 only D) 1 only
 
Answer & Explanation Answer: C) 1 and 2 only

Explanation:

There are two conditions that must be met for an object to be in equilibrium. The first condition is that the net force on the object must be zero for the object to be in equilibrium. If net force is zero, then net force along any direction is zero.

Kinetic energy (KE) is the energy of motion, and kinetic energy is not always conserved in a collision

Energy and momentum are always conserved.

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Q:

Which of the following represents a relation for ‘heat lost = heat gained’?

 

A) Principle of thermal equilibrium B) Principle of colors
C) Principle of calorimetry D) Principle of vaporization
 
Answer & Explanation Answer: C) Principle of calorimetry

Explanation:

Heat lost by hot object = Heat gained by cold object

where we ignore heat gained or lost from/to the surroundings.

The study of heat gained and lost in this manner is often called Calorimetry.

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