物理 2007 年 DSE、CE 選擇題

1.

A bicycle finishes a $100$ -metre journey in $9.77$ s. Assume that the bicycle starts from rest and moves with a uniform acceleration. What is the acceleration of the bicycle throughout the journey ?

2.

Two blocks $A$ and $B$ , of masses $1$ kg and $3$ kg respectively, are placed on a horizontal smooth surface as shown. A horizontal constant force of $12$ N is applied to block $A$ so that the two blocks move to the right with uniform acceleration. What is the magnitude of the contact force between $A$ and $B$ ?

Blocks A and B in contact on a smooth surface, 12 N force pushing A to the right

3.

A skier slides down a slope as shown in the diagram above. Assume constant friction along the slope, which of the following graphs best describes the change of energy of the skier with distance down the slope ?

Four graphs A to D of P.E. and K.E. against distance

4.

A horse pulls a block along a rough horizontal road and moves with a uniform velocity. Which of the following correctly describes the directions of the friction from the ground acting on the horse and the block ?

	Horse	Block
	backward	forward
	backward	backward
	forward	forward
	forward	backward

5.

A child is standing on a weighing scale as shown above. Which of the following pairs of forces is/are (an) action and reaction pair(s) ?

(1)The force exerted by the child on the scale and The force exerted by the scale on the child

(2)The gravitational force exerted by the Earth on the child and The force exerted by the scale on the child

(3)The gravitational force exerted by the Earth on the scale and The gravitational force exerted by Earth on the child

6.

Water has a very high value of specific latent heat of vaporization. Which of the following statements can be illustrated by this fact ?

(1)Water is used as the coolant in car engines.

(2)Coastal region has milder climate as comparing with inland region.

(3)Steam at

100^\circ\mathrm{C}

causes more serious injury to skin than boiling water.

7.

In an experiment, $2$ kg of water at $20^\circ\mathrm{C}$ is heated inside a boiler for $20$ minutes. Water is boiled to $100^\circ\mathrm{C}$ and $1.7$ kg of water remains after boiling. What is the estimated power of the boiler ? Given : Specific heat capacity of water $= 4200\ \mathrm{J\,kg^{-1}\,{}^\circ C^{-1}}$ Specific latent heat of vaporization $= 2.26\times10^6\ \mathrm{J\,kg^{-1}}$

Boiler containing water with a heater connected to the mains supply

8.

The diagram below shows the structure of a cake.

Cross-section of a cake showing sponge cake, whipped egg white with many air bubbles, and ice-cream inside

The ice-cream inside the cake does not melt when it is baked in an oven. Which of the following statements are possible reasons for this phenomenon ?

(1)The whipped egg white is a poor conductor of heat.

(2)The whipped egg white is a good radiator of heat.

(3)The sponge cake is a poor conductor of heat.

9.

Four liquids $P$ , $Q$ , $R$ and $S$ with the same mass are heated at the same rate. The graph below shows the variation of their temperatures with time.

Temperature (0 to 100 degrees C) against time (0 to 20 minutes) for liquids P, Q, R and S

Which liquid has the highest specific heat capacity ?

10.

Pencil lying on a grid in front of a vertical plane mirror, with the eye below

A pencil is placed in front of a vertical plane mirror as shown in the figure above. Which of the following shows the correct position of the image ?

Four grids A to D showing the pencil image in different positions