物理 2001 年 DSE、CE 選擇題

1.

Graph of distance from P against time: straight line decreasing from a positive value to zero

A car travels along a straight road. The variation of the distance of the car from a fixed point $P$ on the road with time is shown above. Which of the following statements is correct ?

2.

A girl walks along a straight road from a point $A$ to a point $B$ with an average speed $1$ m s $^{-1}$ . She then returns from $B$ to $A$ along the same road with an average speed $2$ m s $^{-1}$ . Find the average speed of the girl for the whole journey.

3.

A stone is thrown vertically upwards. Assuming air resistance is negligible, which of the following statements is/are correct ?

(1)The acceleration of the stone decreases throughout the upward motion.

(2)The net force acting on the stone becomes zero when the stone reaches the highest point.

(3)The total energy of the stone remains unchanged throughout the motion.

4.

Photograph of a finger flicking a cardboard with a coin on it resting on a glass

A coin is placed on a piece of cardboard resting on a glass as shown above. If the cardboard is flickered with a finger, the coin will drop into the glass. What does this experiment demonstrate ?

5.

Block on a rough horizontal table with a 10 N force to the right and a 2 N force to the left

A block on a rough horizontal table is acted on by two horizontal forces of magnitudes $10$ N and $2$ N as shown. It remains at rest on the table. If the force of magnitude $10$ N is removed, find the resultant force acting on the block.

6.

Uniform plank on two trestles X and Y, with 1.5 m overhang at each end, 5 m between the trestles, weight 450 N at the middle and a worker standing at the right end

A uniform plane of weight $675$ N stands at one end of the plank as shown above. The worker holds a light basket which contains several packets of goods each of weight $6$ N. What is the maximum number of packets he can hold without tilting the plank ?

7.

Trolley on a friction-compensated runway pulled by force F parallel to the runway; graph of acceleration a against force F is a straight line through the origin

A student uses a friction-compensated runway to study Newton's second law of motion. The variation of the acceleration $a$ of the trolley with the force $F$ applied parallel to the runway is shown above. If the experiment is repeated with the runway making a larger angle of inclination with the horizontal, which of the graphs (in dotted lines) represents the expected result ?

Four graphs A to D, each with the original solid line and a dotted line

8.

Force against time graph with a single hump

The figure above shows the variation of the force acting on a car driver with time when the car hits a wall. The driver is not wearing a seat-belt. Which of the following graphs (in dotted lines) best shows the force acting on the driver if he is wearing a seat-belt ?

Four graphs A to D comparing the original force-time curve (solid) with a dotted curve

9.

A man is pulling a suitcase along the horizontal ground as shown below.

Photograph of a man pulling a suitcase along the ground

Which of the following pairs of forces is/are action and reaction pair(s) according to Newton's third law of motion ?

(1)The gravitational force exerted by the earth on the man and The gravitational force exerted by the man on the earth

(2)The pulling force exerted by the man on the suitcase and The friction exerted by the ground on the suitcase

(3)The gravitational force exerted by the earth on the suitcase and The normal reaction exerted by the ground on the suitcase

10.

A man is pulling a suitcase along the horizontal ground as shown below.

If the rope is inclined at an angle $\theta$ to the horizontal and the tension in the rope is $100$ N, find the work done by the man in pulling the suitcase for a distance of $5$ m along the ground.