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Q:

Hot water is poured simultaneously in four metallic tumblers painted outside with different points. After some time the water will be found to have cooled most in the tumbler painted.

A) rough white B) rough black
C) shining white D) shining black
 
Answer & Explanation Answer: B) rough black

Explanation:

Black  surfaces are good emitters of heat ( They are also good absorbers of heat). If the black surface is rough too, the emitting will be better. So (b) is the correct answer. Shining surfaces reflect back radiation. So if the black surface is also shining the effectiveness of emitting heat is lessened.

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Q:

Frictional force acts in 

A) the same direction as the motion B) the opposite direction of the motion
C) all the directions D) upward direction
 
Answer & Explanation Answer: B) the opposite direction of the motion

Explanation:

It is to overcome this opposite frictional force , that  we have to apply the needed force to make the body move

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Q:

If price of an article decreases from P1 to Rs 25, quantity demanded increases from 900 units to 1200 units. If point elasticity of demand is ­2 find P1?

A) Rs. 20 B) Rs. 30
C) Rs. 25 D) Rs. 35
 
Answer & Explanation Answer: B) Rs. 30

Explanation:
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Q:

A body given with an initial velocity moved under the effect of gravity is called?

Answer

Projectile

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Subject: Physics

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Q:

The wavelength of a wave is the distance between

A) Crest and Trough B) Crest and Crest
C) Trough and Trough D) Both B & C
 
Answer & Explanation Answer: D) Both B & C

Explanation:

Distance between two Consecutive Crests or two Consecutive Troughs is called Wavelength. But the distance between crest and adjacent trough is half the wavelength.

That is the distance between adjacent crest and trough is called Half the wavelength.

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Q:

Heat is associated with

A) K.E of random motion of molecules B) K.E of orderly motion of molecules
C) Total K.E of random and orderly motion of molecules D) None of these
 
Answer & Explanation Answer: A) K.E of random motion of molecules

Explanation:
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Q:

A copper wire of radius r and length lhas a resistance of R. A second copper wire with radius 2r and length lis taken and the two wires  are  joined  in  a  parallel  combination. The  resultant  resistance   of  the  parallel combination of the two wires will be

A) 5 R B) 5 R/4
C) 4 R/5 D) R/5
 
Answer & Explanation Answer: D) R/5

Explanation:

1st copper wire: R = pl/A = pl/ πr2

2ndcopper wire: R’ = p’l’/A’ = pl/(4 πr2) = R/4

If joined in parallel, (1/Req) = (1/R) + (1/R’)

= 1/R + 4/R1/Req= 5/R

Req= R/5

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Q:

The p wave of a normal Electrocardiogram indicates

A) atrial depolarization B) Ventricular repolarization
C) atrial repolarization D) Ventricular depolarization
 
Answer & Explanation Answer: A) atrial depolarization

Explanation:

The P wave in the ECG represents atrial depolarization, which results in atrial contraction, or atrial systole.

The P wave is a summation wave generated by the depolarization front as it transits the atria.

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