Correct Answer: B. poor absorbers and good emitters of radiation

Explanation

Glass and water are made up of molecules. The force of attraction between glass molecules and water molecules is stronger than that among water molecules, hence the resultant force acts upwards leading to the rise of water in the glass tube.

Correct Answer: A. \(\frac{g}{16}\)

Correct Answer: D. α-particles and β-rays and γ-rays

Explanation

(a) A body is said to be moving with uniform acceleration when its time rate of increase of velocity is constant. It is measured in m/s\(^2\). It is a vector quantity.

The above sketch shows the v-t graph of the ball. The velocity decreases uniformly from A to zero (p) at the top of K its flight in a time kp. P , Va It then increases in velocity uniformly as it returns to the point of projection A.

(ii) The magnitude of the slope of the line AP = g or Ap\(^-\) = g, where g = acceleration of free fall due to gravity. The height attained when the ball is thrown up is equal to the area of the triangle AKP. The distance it falls from its maximum height is equal to the area of the triangle A\(^-\)PC which is equal to triangle AKP.

(c)(i) The second stone moves upwards and its acceleration g = 10m/s\(^2\). From equation v = u - gt

10 = 20 - 10t -10 = -10t

t = 1

The second stone has been in air for 1s before they met.

(ii) The first stone has been moving for (1 + 2)s = 3s

From equation v = u + gt

= 2 - (10 x 3) = 20 - 30 = -10m/s

The minus sign means the first stone is moving down and its velocity is 10m/s.

Correct Answer: A. adhesive

Correct Answer: D. the current in a reactance is lower than in the resistance

Correct Answer: D. 24 days

Explanation

(a)

A mass of dry air is entrapped in a uniform capillary tube, sealed at one end, by means of a mercury pellet. Both the tube and thermometer are then firmly attached a half-meter rule and placed in a water bath as shown above. The water is stirred and its temperature \(\theta_{1}\) at a steady state is noted. The corresponding length, \(L_{1}\) of the entrapped air is also noted and recorded. The water is gradually heated and stirred uniformly until another steady temperature, \(\theta_{2}\) is attained and recorded. The corresponding length, \(L_{2}\) of the air column in the capillary tube is again read and recorded. The experiment is repeated to obtain more sets of readings. A graph of L against \(\theta\) is plotted as shown.

Deduction: Since the volume V of the tube is proportional to its length, L the graph shows that the volume of the entrapped air increases (directly) with increase in temperature at constant pressure.

Precautions: Dry air must be used. Also, error of parallax in reading thermometer and meter rule avoided.

(b) \(S = \frac{V_{1} - V_{0}}{V_{0} \theta}\)

= \(\frac{18.7 - 13.7}{13.7 \times 100}\)

= \(\frac{5}{1370}\)

= \(3.65 \times 10^{-3} K^{-1}\)

(c) As temperature increases the kinetic energies the molecules increase and they bombard the wall the container at a faster rate since their velocities has increased. To keep the rate of change of momentum per unit area (i.e pressure) the same, the molecules will have to travel longer distances betweon collision This implies increase in volume.

Correct Answer: B. Efficiency decreases with an increase in friction