1
Q:

A cup of hot coffee is placed on a metal table in a room. By which of the following methods does it lose heat?

A) conduction and convection only B) conduction and radiation only
C) convection and radiation only D) conduction, convection and radiation

Answer:   D) conduction, convection and radiation

Explanation:

Part of the heat is conducted away by the metal table. Convection currents in air near the surface of the coffee are set up which accounts for some heat loss. Heat is also lost by radiation from the hot coffee to the surroundings. Most of the heat is lost by the last method.

Subject: Physics
Q:

The rate of change of linear momentum of a body falling freely under gravity is equal to it's ____ ?

A) Kinetic Energy B) Weight
C) Potential Energy D) Impulse
 
Answer & Explanation Answer: B) Weight

Explanation:

Rate of change of impulse equals the force . In case of freely falling body the only force is the weight.

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3 66
Q:

A disk and a sphere of same radius but different masses roll on two inclined planes of the same altitude and length. Which one of the two objects gets to the bottom of the plane first ?

A) Depends on their masses B) Sphere
C) Disk D) Both reach at the same time
 
Answer & Explanation Answer: B) Sphere

Explanation:

Time does not depend on mass, else

  => is least for 'sphere' and

hence least time is taken by sphere.

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4 197
Q:

A potentiometer wire is 100 cm long and a constant potential difference is maintained across it. Two cells are connected in series first to support one another and then in opposite direction. The balance points are obtained at 50 cm and 10 cm from the positive end of the wire in the two cases. The ratio of the emf's is :

A) 3:4 B) 5:4
C) 5:1 D) 3:2
 
Answer & Explanation Answer: D) 3:2

Explanation:

In series : E1 + E2 = K(50)

In parallel : E1 - E2 = K(10)

E1 + E2 / E1 - E2 = 5/1

=> E1/E2 = 3/2

The emf's are in the ratio of 3:2.

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6 201
Q:

What is the maximum velocity with which a body of mass 'm' must enter a vertical loop of radius 'R'so that it can complete the loop ?

A)    B) gR   C)    D)   

A) A B) B
C) C D) D
 
Answer & Explanation Answer: C) C

Explanation:

To complete the vertical loop, the minimum speed required at the lowest point  =  .

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2 48
Q:

Which of the following group of elements are diamagnetic ?

A) Argon, copper, silver B) Hydrogen, argon, copper
C) Oxygen, copper, silver D) Hydrogen, oxygen, Argon
 
Answer & Explanation Answer: A) Argon, copper, silver

Explanation:
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