JAMB Physics Past Questions & Answers - Page 77

382.

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

B.

150J

C.

50J

D.

200J

Correct 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

383.

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 answer is B

Volume Expansivity \(\gamma\) = \(3\alpha\)

\(\gamma = 3 \times 2\times10^{-5}\)

\(\gamma = 6\times10^{-5}C^{-1}\)

\(V_{2} = V_{1}(1 + \gamma\theta)\)

\(V_{2} = 15( 1 + (6\times10^{-5}\times(100-0)))\)

\(V_{2} = 15(1.006)\)

= \(15.09cm^{3}\)

384.

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 answer is A

No explanation has been provided for this answer.

385.

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 answer is C

No explanation has been provided for this answer.