Physics questions and answers

Physics Questions and Answers

If you want to learn more about the nature and properties of matter and energy or you're simply preparing for a Physics exam, these Physics past questions and answers are ideal for you.

396.

In the figure, the value of R is 

A.

3\(\Omega\)

B.

6\(\Omega\)

C.

4\(\Omega\)

D.

5\(\Omega\)

Correct answer is B

R\(_T\) = \(\frac{V}{1} = \frac{12}{2}\) = 6\(\Omega\) 

R\(_T\) = 3 + \(\frac{R \times 6}{R + 6}\) 

R = 6\(\Omega\) 

397.

In an experiment in which molten naphthalene is allowed to cool, the cooling curve i n the figure was obtained. The temperature 80\(^o\)C is known as the 

A.

cooling temperature

B.

boiling point

C.

melting point

D.

vaporization point

Correct answer is C

No explanation has been provided for this answer.

398.

The fiqure above represents a block-and-tackle pulley system on which an effort of W Newtons supports a load of 120.0N. If the efficiency of the machine is 40\(^o\), then the value of W is 

A.

28.0N

B.

48.0N

C.

288.0N

D.

50.0N

Correct answer is D

V.E = 6, load = 120N 

Efficiency = M.A x \(\frac{1}{V.R}\) x 100%

40 = \(\frac{120}{effort}\) x \(\frac{1}{6}\) x \(\frac{100}{1}\) 

Effort = 50N

399.
400.

Heat is supplied uniformly at the rate of 100W to 1.0 x 10\(^{-2}\)kg of a liquid for 20 seconds. If the temperature of the liquid rises by 5\(^o\)C, then the specific heat capacity of the liquid is 

A.

2.0 x 10\(^2\)Jkg\(^-1\)K\(^-1\)

B.

2.0 x 10\(^2\)Jkg\(^-1\)

C.

4.0 x 10\(^4\)Jkg\(^-1\)K\(^-1\)

D.

4.0 x 10\(^4\)Jkg\(^-1\)

Correct answer is C

Heat energy = Electrical Energy 

MC\(\theta\) = power x time 

5 x 1 x 10\(^{-2}\) x C = 100 x 20 

C = \(\frac{200}{5 \times 10^2}\) 

= 4 x 10\(^4\) J/kg/\(^oC\)