物理 2009 年 DSE、CE 選擇題

1.

A car is travelling at a constant speed of $50$ km h $^{-1}$ . How much time does it take to travel $500$ m ?

2.

The figure above shows three paths $P_1$ , $P_2$ and $P_3$ from $X$ to $Y$ on a horizontal plane. Three students take the same time to travel from $X$ to $Y$ via the three paths respectively. Which of the following physical quantities about their journey is/are the same ?

(1)displacement

(2)distance

(3)average speed

3.

A ball of mass $0.5$ kg resting on a horizontal ground is kicked by a player. The ball travels along a straight path and come to rest after travelling a horizontal distance of $10$ m. If the average resistive force acting on the ball during the motion is $3$ N, what is its initial speed ?

4.

A block of mass $1$ kg rests on a rough horizontal plane. When it is pulled by a horizontal force of $5$ N, it moves with an acceleration of $2\ \mathrm{m\,s^{-2}}$ . Now, the block is at rest and is pulled by a horizontal force of $2$ N, what is the resultant force acting on the block ?

5.

John and Mary are driving two cars, $P$ and $Q$ , along a straight horizontal road respectively. At time $t = 0$ , they both see an obstacle and apply the brakes to stop the cars with uniform deceleration. The variation of velocity with time of the two cars is shown in the figure below. Which of the following statements is/are correct ?

(1)The two cars have the same initial speeds.

(2)The reaction times of John and Mary are the same.

(3)The total stopping distances of the two cars are the same.

Velocity-time graphs of P (higher initial speed) and Q, both constant for the same reaction time then decreasing linearly to zero at the same time

6.

Force F pushing a block on a horizontal smooth surface

A constant force $F$ is applied to an object which is initially at rest on a horizontal smooth surface. Which of the graphs below best represents the variation of the power $P$ developed by the force $F$ with time $t$ ?

Four graphs A to D of power P against time t

7.

Square grid with the resultant force F and force F1 drawn from a point

Force $F$ is the resultant of two forces $F_1$ and $F_2$ on a horizontal plane. Which of the following diagrams best represents the missing force $F_2$ ?

Four grids A to D each showing a candidate force F2

8.

An object of weight $120$ N on the Earth's surface is taken to the Moon's surface where the acceleration due to gravity is $\dfrac{1}{6}$ of that at the Earth's surface. What are the mass and the weight of the object at the Moon's surface ? (Take the acceleration due to gravity on the Earth's surface to be $10\ \mathrm{m\,s^{-2}}$ .)

	mass	weight
	$2$ kg	$20$ N
	$2$ kg	$120$ N
	$12$ kg	$20$ N
	$12$ kg	$120$ N

9.

Which of the following descriptions about internal energy are correct ?

(1)Different masses of water at the same temperature have the same amount of internal energy.

(2)A copper block has greater internal energy when it is hot than when it is cold.

(3)Water at

0^\circ\mathrm{C}

has greater internal energy than a block of ice of the same mass at

0^\circ\mathrm{C}

.

10.

Some ice cubes at $0^\circ\mathrm{C}$ are added to $0.3$ kg of soft drink at $20^\circ\mathrm{C}$ . What is the minimum amount of ice needed to cool the soft drink to $0^\circ\mathrm{C}$ ? Given : specific heat capacity of the soft drink $= 5300\ \mathrm{J\,kg^{-1}\,{}^\circ C^{-1}}$ specific latent heat of fusion of ice $= 3.34\times10^5\ \mathrm{J\,kg^{-1}}$