JAMB Physics Past Questions & Answers - Page 15

71.

Find the tension in the two cords shown in the figure above. Neglect the mass of the cords, and assume that the angle is 38° and the mass m is 220 kg

[Take g = 9.8 ms-2]

A.

\(T_1\) = 2864 N, \(T_2\)= 3612 N

B.

\(T_1\)= 3612 N, \(T_2\) = 2864 N

C.

\(T_1\)= 3502 N, \(T_2\)= 2760 N

D.

\(T_1\) = 2760 N, \(T_2\) = 3502 N

Correct answer is C

W =  mg  = 220 x 9.8 = 2156 N


⇒Sin 38º = \(\frac{2156}{T_1}\)

⇒ \(T_1\) =    \(\frac{2156}{Sin 38}\)

⇒ \(T_1\) =     3502 N

 

Cos 38º =  \(\frac{T_2}{T_1}\)

⇒ \(T_2\)  =   3502 x Cos 38º

⇒ \(T_2\) =   2760 N

 

;    \(T_1\) =   3502 N,  \(T_2\) = 2760 N.

 

 

72.

Which of the following statements regarding the application of electrical conduction via gases is/are correct?
Electrical conduction in gas is applied in:
(i) The identification of gases
(ii) Lighting/fluorescent tubes
(iii) Photocells
(iv) Cathode ray oscilloscope/T.V. tubes

A.

(i), (iii) and (iv) only

B.

(i), (ii) and (iv) only

C.

(ii), (iii) and (iv) only

D.

(i), (ii) and (iii) only

Correct answer is B

Electrical conduction of gas is applied in:
(i) The identification of gases
(ii) Lighting/fluorescent tubes
(iii) Advertising industry/Neon signs
(iv) Cathode ray oscilloscope/T.V. tubes

73.

The property of wave shown in the diagram above is?

A.

Diffraction

B.

Refraction

C.

Polarisation

D.

Interference

Correct answer is A

Diffraction is the bending of waves around the corners of an obstacle or through an aperture.

74.

If an object just begins to slide on a surface inclined at 30º to the horizontal,the coefficient of friction is?

A.

√3

B.

\(\frac{√3}{2}\)

C.

\(\frac{1}{√2}\)

D.

\(\frac{1}{√3}\)

Correct answer is D

A body sliding down a plane inclined at 30o to the horizontal,

Has coefficient of friction = tan 30º  or \(\frac{1}{√3}\)

75.

The mercury column in the barometer at notational  atmospheric pressure has a height of?

A.

0.76 cm at see level

B.

760 cm at sea level

C.

7.6 cm at sea level

D.

76 cm at sea level

Correct answer is D

The height of the mercury column serves as an indicator of atmospheric pressure. At sea level and at a temperature of 0° Celsius (C), the height of the mercury column is approximately 30 inches, or 76 centimeters. This represents a pressure of approximately 14.7 psia. The 30-inch column is used as a reference standard.