物理 1994 年 DSE、CE 選擇題

1.

Which of the following is a correct unit for the corresponding physical quantity ?

	Physical quantity	Unit
	Work	watt
	Electromotive force	newton
	Momentum	newton second
	Heat capacity	joule per kilogram

2.

Paper tape with evenly spaced dots, pulled to the right

A trolley is given a push and runs down a friction-compensated runway. The motion of the trolley is recorded on the paper tape as shown above. Which of the following changes can enable the trolley to produce a paper tape as shown below :

Paper tape with more widely spaced dots, pulled to the right

(1)Giving the trolley a harder initial push.

(2)Increasing the angle of inclination of the runway.

(3)Increasing the frequency of the ticker-tape timer.

3.

Block Y hung from the ceiling by string T2 and block X hung below Y by string T1, with a 4 N downward force on X

Two blocks $X$ and $Y$ of weights $2$ N and $8$ N respectively are suspended by two light strings as shown in the diagram. A downward force of $4$ N is applied to $X$ . Find the tensions $T_1$ and $T_2$ in the two strings.

	$T_1$	$T_2$
	$4$ N	$10$ N
	$4$ N	$14$ N
	$6$ N	$12$ N
	$6$ N	$14$ N

4.

A man takes $30$ s to walk $80$ m towards the east. He then takes $10$ s to run $60$ m towards the south. Which of the following statements is/are correct ?

(1)The magnitude of the resultant displacement of the man is

140

m.

(2)The average speed of the man is

4.3

m s

^{-1}

.

(3)The magnitude of the average velocity of the man is

2.5

m s

^{-1}

.

5.

A man of mass $50$ kg is standing in a lift. If the lift is falling freely, which of the following statements is/are true ?

(1)The weight of the man is

0

N.

(2)The force acting on the floor of the lift by the man is

491

N.

(3)The force acting on the man by the floor of the lift is

0

N.

6.

Light rod PQRST with points 10 cm apart: 2 N downward at R and 2 N upward at T

The above diagram shows a light rod under the action of two vertical forces. Under which of the following conditions will the rod be in equilibrium ?

7.

A stone is projected vertically upwards. Neglecting air resistance, which of the following graphs shows the variation of the kinetic energy $KE$ of the stone with the distance travelled $s$ during its upward motion ?

Four graphs A to D of KE against distance s

8.

Two blocks $X$ and $Y$ are connected by a light string passing over a smooth pulley as shown. The mass of $X$ is greater than that of $Y$ . The two blocks are released from rest. Which of the following statements is/are correct ?

(1)The potential energy lost by

X

is equal to the potential energy gained by

Y

.

(2)The kinetic energy gained by

X

is greater than the kinetic energy gained by

Y

.

(3)The potential energy lost by

X

is equal to the sum of kinetic energies gained by

X

and

Y

.

Blocks X and Y hanging on either side of a smooth pulley

9.

Which of the following statements concerning real images formed by a lens is/are correct ?

(1)Real images are always diminished.

(2)Real images can be photographed with a camera.

(3)Without a screen, real images cannot be seen by the eye.

10.

Which of the following devices involve(s) total internal reflection of light as they work ?

(1)Optical fibres

(2)A prismatic periscope

(3)A plane mirror