物理 2011 年 DSE、CE 選擇題

1.

Ball moving along a smooth curved rail through points P, Q, R, S and T

A ball moves along a smooth curved rail and passed $P$ at a certain speed as shown in the figure above. Neglecting air resistance and friction, which of the following statements about the motion of the ball are correct ?

(1)The ball has maximum kinetic energy at

R

.

(2)The speed of the ball at

S

is the same as that at

Q

.

(3)The ball can never reach

T

.

2.

Questions 3 and 4 : A man of mass $50$ kg stands still on a balance in a lift which is initially moving downwards. Between $t=0$ and $6$ s, the reading $R$ on the balance varies with time as shown in the graph below. Take $g$ to be $10\ \mathrm{m\,s^{-2}}$ .

Graph of balance reading R / N against t / s: 400 N from 0 to 3 s, then 500 N from 3 s to 6 s

Which of the following statements is/are correct ?

(1)Between

t=0

and

3

s, the net force acting on the man is

400

N.

(2)At

t=3

s, the lift starts to move upwards.

(3)Between

t=3

s and

6

s, the lift is moving at a constant velocity.

3.

Questions 3 and 4 : A man of mass $50$ kg stands still on a balance in a lift which is initially moving downwards. Between $t=0$ and $6$ s, the reading $R$ on the balance varies with time as shown in the graph below. Take $g$ to be $10\ \mathrm{m\,s^{-2}}$ .

What is the acceleration of the lift between $t=0$ and $3$ s ?

4.

Block on a horizontal surface pushed by a horizontal force F

On a horizontal surface, horizontal force $F$ is exerted on a block as shown in the figure above. When $F=25$ N, the block remains at rest. Which of the following statements must be correct ?

5.

Photograph of an ant hanging upside down from the ceiling holding a block in its jaws

The photo above shows an ant hanging upside down from the ceiling. The ant is holding a $500$ mg block using its jaws. At the ceiling, the ant and the block are at rest. Which of the following statements is/are correct ?

(1)The force acting on the ant by the ceiling points upwards.

(2)The force acting on the block by the ant and the weight of the block are an action and reaction pair.

(3)The net force acting on the ant is zero.

6.

Graph of kinetic energy against t squared, a straight line through the origin reaching 15000 J at t squared = 5

A car of mass $1500$ kg is accelerating from rest along a straight road. The above figure shows the variation of its kinetic energy (K.E.) with the square of time $t$ . What is the acceleration of the car ?

7.

Two liquids $X$ and $Y$ are heated by two different heaters. The energy supplied, the mass of the liquid and the temperature rises are recorded as follows.

	Liquid $X$	Liquid $Y$
Energy supplied / J	24000	18000
Mass / kg	0.3	0.2
Temperature rise / $^\circ$ C	20	25

Which of the following statements are correct ?

(1)The heat capacity of

X

is larger than that of

Y

.

(2)The specific heat capacity of

X

is larger than that of

Y

.

(3)The heat capacity of

X

determined remains the same if the experiment is repeated by doubling the mass of

X

.

8.

Questions 54 and 55 : The setup in Figure (a) is used to determine the specific latent heat of fusion of ice. At time $t=0$ , $0.15$ kg of ice cubes at $0^\circ\mathrm{C}$ are added into $1$ kg of hot water. The initial temperature of water is $60^\circ\mathrm{C}$ . Figure (b) shows the variation of the water temperature with time. At $Q$ , the mixture achieves the thermal equilibrium.

Figure (a): beaker of water with thermometer and ice cubes; Figure (b): temperature falling from 60 degrees C at P through 40 degrees C at Q towards 20 degrees C at R

What is the specific latent heat of fusion of ice estimated from this experiment ? Given : specific heat capacity of water $= 4200\ \mathrm{J\,kg^{-1}\,{}^\circ C^{-1}}$

9.

Questions 54 and 55 : The setup in Figure (a) is used to determine the specific latent heat of fusion of ice. At time $t=0$ , $0.15$ kg of ice cubes at $0^\circ\mathrm{C}$ are added into $1$ kg of hot water. The initial temperature of water is $60^\circ\mathrm{C}$ . Figure (b) shows the variation of the water temperature with time. At $Q$ , the mixture achieves the thermal equilibrium.

Which of the following statements about the experiment is correct ?

10.

As shown in the figure, a $2$ W light bulb is immersed into $50$ g of water. The bulb is operating at its rated value. After $10$ minutes, the temperature of the water increases by $4.5^\circ\mathrm{C}$ . Estimate the amount of light emitted during the $10$ minutes. Given : specific heat capacity of water $= 4200\ \mathrm{J\,kg^{-1}\,{}^\circ C^{-1}}$

Light bulb immersed in water in a transparent plastic cup with foam cover and thermometer