物理 1991 年 DSE、CE 選擇題（第 2 頁）

11.

Two particles $A$ and $B$ of masses $2$ kg and $1$ kg respectively move in opposite directions. The initial velocity of $A$ is $4\ \mathrm{m\,s^{-1}}$ towards the right, while that of $B$ is $2\ \mathrm{m\,s^{-1}}$ towards the left. They collide head on. After the collision, the velocity of $A$ becomes $1\ \mathrm{m\,s^{-1}}$ towards the right. What would be the velocity of particle $B$ ?

Particle A moving right at 4 m/s and particle B moving left at 2 m/s

12.

Object O and its upright image I with points A, B, C and D on the axis

In the diagram, the image $I$ of an object $O$ is produced by a lens. What is the nature and position of this lens ?

13.

$Converging lens forming an image of an object, with refracted rays P, Q, S and T drawn$

In the figure above, $F$ is the focus of the converging lens. Which of the refracted rays is INCORRECTLY drawn ?

14.

Which of the following can increase the average kinetic energy of the molecules of a fixed mass of gas ?

(1)Heating the gas at constant volume

(2)Increasing the volume of the gas at constant pressure

(3)Reducing the volume of the gas at constant temperature

15.

Which of the following graphs correctly shows the variation of volume $V$ with absolute temperature $T$ of a fixed mass of gas at constant pressure ?

Four graphs of V against T: A straight line falling, B straight line rising from the origin with dashed extension, C rising line with dashed extension to negative T, D rising line crossing the V axis

16.

Temperature against time graph on a grid, time axis marked 0, 200, 400, 600 s, with a flat section

A $400$ W electric heater is used to heat $0.4$ kg of a solid. The graph shows the temperature against time of the substance. The specific latent heat of fusion of the substance is

17.

Which of the following statements concerning the Brownian motion of smoke particles in air is/are correct ?

(1)The Brownian motion is caused by collision between smoke particles.

(2)The air molecules are moving randomly in all directions.

(3)The mass of air molecules is almost the same as that of smoke particles.

18.

The apparatus shown is used to study the relation between the temperature and the pressure of a gas at constant volume. Which of the following is NOT correct ?

Flask of gas connected to a Bourdon gauge, immersed in a beaker of water with stirrer and thermometer

19.

Water wave travelling to the right with particles P, Q, R and S marked

The above diagram shows a water wave travelling to the right. Which of the following statements is/are true ?

(1)

PQ

is equal to the wavelength.

(2)

PR

represents the amplitude.

(3)The particle at

P

will move to

S

after a quarter of a period.

20.

Vibrator attached to a string, one complete vibration made, wave travelling to the right

A vibrator of frequency $5$ Hz generates waves on a string. The above diagram shows the shape of the string at the instant when the vibrator has made one complete vibration. Which of the following best shows the waveform $0.1$ s later ?