物理 1990 年 DSE、CE 選擇題

1.

The graph shows how the square of velocity of an object undergoing uniform acceleration varies with displacement. The object is initially at rest and travels along a straight line. The acceleration of the object is

Graph of v squared against s: straight line from the origin to 6 m^2/s^2 at s = 3 m

2.

A block of mass $5$ kg is moving horizontally on a smooth surface along a straight line at $6\ \mathrm{m\,s^{-1}}$ . In order to change its speed to $10\ \mathrm{m\,s^{-1}}$ , the work done would need to be

3.

Ticker-tape timer, trolley moving along a horizontal surface and a lump of plasticine above it

A trolley moves with constant speed along a horizontal surface. A lump of plasticine having the same mass as the trolley is dropped onto the trolley and sticks to it. Which one of the following ticker-tape best represents the motion of the trolley ?

Four ticker-tapes A to D with printed dots

4.

$Y$ has a linear relationship with time as shown. $Y$ may represent

(1)the speed of a body starting from rest under a constant force.

(2)the distance travelled by a body at constant speed.

(3)the acceleration of a body falling from rest.

Graph of Y against Time: straight line through the origin

5.

Two objects $P$ and $Q$ , of mass $0.1$ kg and $0.5$ kg respectively, are thrown vertically upwards with the same speed from the same level. Neglecting air resistance, which of the following is true ?

6.

Which of the following statements is/are correct when a collision between two particles is elastic ?

(1)None of the original kinetic energy is converted into other forms of energy.

(2)The linear momentum of each particle is conserved.

(3)The mechanical energy of each particle is conserved.

7.

A small metal ball is released from a point above the floor and bounces several times. Which of the following graphs best represents the variation of the velocity of the ball with time ?

Four graphs A to D of velocity v against time t

8.

Uniform metre rule hung by a string with tension T, a 6 N weight 30 cm from the left end and a weight W at the right end, the string 20 cm from the 6 N weight

In the figure shown, the uniform metre rule of weight $1$ N is balanced horizontally. Find the tension $T$ in the string.

9.

What happens to the wavelength and frequency of a ray of light if it passes from water to air ?

	Wavelength	Frequency
	increases	decreases
	decreases	remains unchanged
	remains unchanged	increases
	increases	remains unchanged

10.

If $F$ , $F'$ are foci and $C$ , $C'$ are both at a distance of two times the focal length from the lens, which of the following ray diagrams is/are correct ?

Three ray diagrams (1), (2), (3) for a concave lens