JAMB Physics Past Questions & Answers - Page 16

76.

One of the following is a scalar quantity?

A.

weight

B.

momentum

C.

potential energy

D.

displacement

Correct answer is C

Examples of scalar quantities are mass, energy, distance, charge, volume, time, speed, and the magnitude of physical vectors in general

77.

A semiconductor is formed by?

A.

co-ordinate bonds

B.

electrovalent bonds

C.

a substance free of bonds

D.

covalent bonds

Correct answer is D

It's generally created using silicon, germanium, or other pure elements.

Semiconductors are created by adding impurities to the element.

The conductance or inductance of the element depends on the type and intensity of the added impurities.

The electrons surrounding each atom in a semiconductor are part of a covalent bond

78.

The main factor which affects the speed of sound wave is the?

A.

properties of the medium

B.

amplitude of the sound wave

C.

intensity of the sound wave

D.

loudness of the sound wave

Correct answer is A

Factors Affecting The Speed of Sound

  • The Density of Medium: Sound requires a medium to travel. The density of the medium is among the factors which affect the speed of sound. ...
  • The Temperature of The Medium: Higher the temperature, the higher is the speed of sound in the medium.

79.

A train of mass 1600 kg attains a speed of 25 ms\(^{-1}\) in 20 seconds. The power developed in the engine is?

A.

2.5 KW

B.

80 KW

C.

25 KW

D.

50 KW

Correct answer is D

where force = f, mass = m, acceleration = a, velocity = v, time = t

Force = m * a → m * \(\frac{Δv}{t}\) 

Power = f * v

P = m * \(\frac{v}{t}\)  * v = m * \(\frac{v^2}{t}\) 

p =  \(\frac{1600 * 25^2}{20}\) 

p = 50,000 or 50 KW

80.

What quantity of heat is required to convert 20 g of ice at 0 ºC to water at the same temperature? (Specific latent heat of ice = 336 Jg\(^{-1}\))

A.

7.06 x 10\(^{3}\)J

B.

5.38 x 10\(^{3}\)J

C.

6.72 x 10\(^{3}\)J

D.

1.35 x 10\(^{3}\)J

Correct answer is C

quantity of heat = mass * Specific latent heat → 20 * 336 

quantity of heat = 6720j or  6.72 x 10\(^{3}\)J