21. The pitch of an acoustic device can be increased by
- A. decreasing the loudness
- B. increasing the intensity
- C. increasing the frequency
- D. decreasing the intensity
Correct Option: Answer is C
22. One of the features of the fission process is that
- A. it leads to chain reaction
- B. its products are not radioactive
- C. neutrons are not released
- D. the of the masses of the reactants equals the sum of the masses of the products
Correct Option: Answer is A
23. The linear expansivity of brass is 2 x 10\(^{-5}\) C\(^{-1}\). If the volume of a piece of brass is 15.00cm at 0°C, what is the volume at 100°C
- A. 16.03cm\(^3\)
- B. 15.09cm\(^3\)
- C. 16.00cm\(^3\)
- D. 15.03cm\(^3\)
Correct Option: Answer is B
Volume Expansivity \(\gamma\) = \(3\alpha\)
\(\gamma = 3 \times 2\times10^{-5}\)
\(\gamma = 6\times10^{-5}C^{-1}\)
\(V_{2} = V_{1}(1 + \gamma\theta)\)
\(V_{2} = 15( 1 + (6\times10^{-5}\times(100-0)))\)
\(V_{2} = 15(1.006)\)
= \(15.09cm^{3}\)
24. A lead bullet of mass 0.05 kg is fired with a velocity of 200 m/s into a lead block of mass 0.95 kg. Given that the lead block can move freely, the final kinetic energy after impact is
- A. 100J
- A. 150J
- C. 50J
- D. 200J
Correct Option: Answer is C
From the law of conservation of linear momentum,
\(m_1 u_1 + m_2 u_2 = m_1 v_1 + m_2 v_2\)
Since the collision is inelastic, we have
\((0.05 \times 200) – (0.95 \times 0) = (0.05 + 0.95)V\)
\(10 = V\)
\(V = 10ms^{-1}\)
Hence the Kinetic energy = \(\frac{1}{2} (0.05 + 0.95) \times 10^2\)
= \(\frac{1}{2} \times 100\)
= 50J
25. In a series R-L-C circuit at resonance, the voltages across the resistor and the inductor are 30V and 40V respectively. What is the voltage across the capacitor?
- A. 30V
- B. 70V
- C. 50V
- D. 40V
Correct Option: Answer is D
26. If the fraction of the atoms of a radioactive material left after 120years is , what is the half-life of the material?
- A. 20 years
- B. 10 years
- C. 2 years
- D. 24 years
Correct Option: Answer is A
27.
In the diagram shown, which of the simple pendulum will resonate with P when set into oscillation?
- A. U
- B. T
- C. R and T
- D. Q and R
Correct Option: Answer is B
28. The time rate of loss of heat by a body is proportional to the
- A. temperature of its surroundings
- B. temperature of the body
- C. difference in temperature between the body and its surroundings
- D. ratio of the temperature of the body to that of its surroundings
Correct Option: Answer is C
29. A positively charged rod X is brought near an uncharged metal sphere Y and is then touched by a finger with X still in place. When the finger is removed, the result is that Y has
- A. no charge and a zero potential
- B. a positive charge and a zero potential
- C. a negative charge and a positive potential
- D. a negative charge and a negative potential
Correct Option: Answer is D
30. Electrical appliances in homes are normally earthed so that
- A. a person touching the appliances is safe from electric shock
- B. both the a.c. and d.c. sources can be used
- C. the appliances are maintained at a higher pd than the earth
- D. the appliances are maintained at a lower pd than the earth