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.

4,076.

In the diagram above a beam of white light travels from a rare to a dense medium. What colours of light do the rays a, b and c respectively represents?

A.

red, green and blue

B.

Green, red and blue

C.

Yellow , blue and red

D.

Blue , yellow and red

Correct answer is A

No explanation has been provided for this answer.

4,077.

The diagram above shows two capacitors P and Q of capacitance 5μF and 10μF. Find the charges stored in P and Q respectively

A.

2μC and 4μC

B.

4μC and 2μC

C.

100μC and 200μC

D.

200μC and 100μC

Correct answer is C

Since capacitance C = Q/V, => Q = CV
∴ Qp = 5 x 10-b x 20
= 100 x 10-b or 100μC
Qp = 10 x 10-b x 70
= 200 x 10-b or 200μC
Correct option 100μC and 200μC

4,078.

A transverse wave is applied to a string whose mass per unit length is 3 x 10-2kgm-1. If the string is under a tension 12N, the speed of the propagation of the wave is

A.

5 ms-1

B.

20 ms-1

C.

30 ms-1

D.

40 ms-1

Correct answer is B

For transverse wave on string
velocity V = √T/M
where T is the tension, and M is the mass per unit length
∴ for T = 12N and M = 3.0 x 10-2kgm-1
V=
√ 12 / (3.0x10-2

=
√ 12 / 0.03

=
√ 1200 / 3

=
√ 1200 / 3 = 20

∴V = 20m/s

4,079.

A travelling wave moving from left to right has an amplitude of 0.15m, a frequency of 550Hz and a wavelength of 0.01m. The equation describing the wave is

A.

y = 0.15 sin 200π(x - 5.5t)

B.

y = 0.15 sin π(0.01x - 5.5t)

C.

y = 0.15 sin 5.5π(x - 200t)

D.

y = 0.15 sin π(550x - 0.01t)

Correct answer is A

The general wave equation is given by Y = sin A /λ [x - vt]
= Sin A [(2π X)/λ - (2π vt)/λ]
thus if A = 0.15;λ = 0.01m; f = 550Hz
then V = f x λ = 550 x 0.01 = 5.50m/s
∴ Y = 0.15 sin [(2 x λ x X)/0.01 - (2 x λ x 5.5t)/0.01]
= 0.15 sin[200λX - 200 x λ x 5.5t]
∴ Y = 0.15 sin 200λ[x - 5.5t]

4,080.

A sonometer wire is vibrating at frequency fo. If the tension in the wire is doubled while the length and the mass per unit length are kept constant, the new frequency of vibration is

A.

fo/2

B.

2fo

C.

fo/√2

D.

fo√2

Correct answer is D

For a vibrating sonometer wire, the frequency
F = l/2l √(T/m)
and if the length, l and mass per unit length, m, are constant, then Fo ∝ √T => FoK√T or Fo/√T = K
=> F1o/√F1 = F2o/√F2
∴ F1o/√T1 = F2o/√T2

thus F2 = F3x√(2T1
__√T1


=

= Fox√2 x √T1
√T1


∴F2 = Fo x √2 = Fox√2