物理 2003 年 DSE、CE 選擇題

1.

Questions 1 and 2 : The figure shows the velocity-time graph of a car travelling along a straight road.

Velocity-time graph with the area between the graph and the time axis shaded from t = 0 to t1, then negative velocity from t1 to t2

What physical quantity does the area of the shaded region represent ?

2.

Questions 1 and 2 : The figure shows the velocity-time graph of a car travelling along a straight road.

Which of the statements are correct ?

(1)The car changes its direction of travel at

t = t_1

.

(2)The car is farthest away from the starting point at

t = t_1

.

(3)The car returns to its starting point at

t = t_2

.

3.

A car starts at point $A$ and travels along a circular path of radius $30$ m. After $15$ s, the car returns to point $A$ . Find the average speed of the car within this period of time.

Circular path of radius 30 m starting and ending at point A

4.

A plane starts from rest and accelerates at $2$ m s $^{-2}$ . If the minimum take-off speed is $60$ m s $^{-1}$ , find the minimum distance travelled by the plane before it takes off.

5.

Block sliding down an inclined plane at angle theta

A block of mass $m$ slides down an inclined plane with uniform velocity. What is the net force acting on the block ?

6.

Amusement park ride: a seat raised to the top of a vertical pole, with point P near the ground

The figure shows a ride in an amusement park. A passenger is fastened to a seat which is then raised to the top of a vertical pole. At time $t=0$ , the seat is released from rest and falls freely. After $3$ s, the seat is brought to rest at a point $P$ near the ground. Which of the below graphs best shows the relation between the gravitational force acting on the passenger $W$ and $t$ ?

7.

Uniform cube held by four cables, each making 20 degrees with the vertical

A uniform cube of weight $600$ N is held in equilibrium in the air by four identical cables as shown above. If each cable makes an equal angle of $20^\circ$ with the vertical, find the tension in each cable.

8.

Photograph of a child sitting in a safety seat

A car accelerates at $3\ \mathrm{m\,s^{-2}}$ along a straight horizontal road. A child of mass $10$ kg is sitting on a safety seat inside a car. Find the magnitude of the resultant force exerted by the safety seat on the child. (Take the acceleration due to gravity to be $10\ \mathrm{m\,s^{-2}}$ .)

9.

Wooden block hanging from a ceiling by a string with a bullet approaching it horizontally

A wooden block of mass $M$ is hanging freely in the air from a light string of length $L$ . A bullet, of mass $m$ travelling at a speed $v$ , hits the block and becomes embedded in it. The block then swings upwards. Which of the following are employed in determining the maximum height reached by the block ?

(1)Newton's first law

(2)Law of conservation of energy

(3)Law of conservation of momentum

10.

Uniform rod hung by two spring balances P and Q: P is 0.2 m from the left end, 0.5 m between P and Q, Q is 0.3 m from the right end

A uniform rod of weight $50$ N is supported by two spring balances $P$ and $Q$ and remains at rest as shown above. Assume the weight of the rod acts through its mid-point. Find the readings of $P$ and $Q$ .

	Reading of $P$	Reading of $Q$
	$17$ N	$33$ N
	$20$ N	$30$ N
	$30$ N	$20$ N
	$33$ N	$17$ N