JAMB Physics Past Questions & Answers - Page 148

736.

The colours seen on soap bubbles are due to

A.

Diffraction

B.

Refraction

C.

Dispersion

D.

Interference

Correct answer is D

No explanation has been provided for this answer.

737.

If the total force acting on a particle is zero, the linear momentum will

A.

Increase

B.

Decrease

C.

Be Constant

D.

Increase then decrease

Correct answer is C

No explanation has been provided for this answer.

738.

In a fission process, the decrease in mass is 0.01%. How much energy could be obtained from the fission of 0.1g of the material

A.

\( 9.0 \times 10^{9}J \)

B.

\( 9.0 \times 10^{10}J \)

C.

\( 6.3 \times 10^{11}J \)

D.

\( 9.0 \times 10^{11}J \)

Correct answer is A

In general, the energy released during nuclear fission is given by the Einstein's mass-energy equation, given by

\( E = \Delta MC^2 \)

Where \( \Delta m\) is the mass defect, and C is the speed of light.
Therefore
\( \Delta m = 0.01% \text{of} 1.0g = \frac{0.01}{100}
\times 1.0g \\

= 1.0 \times 10^{-4} \\
= 1.0 \times 10^{-7}kg\\

\text{Energy Released } = \Delta MC^2 \\

= 1.0 \times 10^{-7} \times (3.0 \times 10^8)^2\\
= 1.0 \times 10^{-2} \times 9.0 \times 10^{16} \\

= 9.0 \times 10^9 J \)

739.

If the uncertainty in the measurement of the position of a particle is 5.0 x 10-10m, the uncertainty in the momentum of the particle is

A.

1.32 x 10-44Ns

B.

3.30 x 10-44Ns

C.

1.32 x 10-24Ns

D.

3.30 x 10-24Ns

Correct answer is C

From the uncertainty principle the product of the position and momentum of a sub-atomic particle is equal or greater than planck's constant.

i.e \( \Delta x. \Delta p \geq h. \\
\text{Thus} 5 \times 10^{-10} \times \Delta p = 6.6 \times 10^{-34} \\

\Delta p = \frac{6.6 \times 10^{-34}}{5 \times 10^{-10}} = 1.32 \times 10^{-24}Ns\\

\text{Therefore Uncertainty in the momentum } = 1.32 \times 10^{-24}Ns \)

740.

Given that young's modulus for aluminium is 7.0 x 1010Nm-2 and density is 2.7 x 103kgm-3 find the speed of the sound produced if a solid bar is struck at one end with a hammer

A.

5.1 x 103ms-1

B.

4.2 x 103ms-1

C.

3.6 x 103ms-1

D.

2.8 x 103ms-1

Correct answer is A

The speed of sound in a material is given as:

\( V = \sqrt{\frac{E}{P}}, Where\\

E = \text{Young's modulus} \\
P = \text{Density }\\

\text{Therefore } V = \sqrt{\frac{7.0 \times 10^{10}}{2.7 \times 10^3}} = 5091.75\\

= 5.1 \times 10^3MS^{-1} \)