Physics Form 4 -- Chapter 2

Analysing Linear Motion (直线运动分析)

1. - Distance - (距离)

Distance is a scalar quantity which has only magnitude but no direction

=距离是一个scalar quantity(标量)，但它只有大小没有方向

2. - Displacement - (位移,换置)

Displacement is a vector quantity which has both magnitude and direction . 

=位移是一个vector quantity(矢量) , 有大小和方向。

3. - Speed - (速度)

Speed is defined as the distance travelled per unit time

=速度定义为距离÷行驶时间

4. - Velocity - (速度)

Velocity of an object is defined as the distance per unit time in a specified direction . Velocity is measured in meter per second (m/s)

=一个物体的速度定义为在一个指定的方向的距离÷时间。

5. - Acceleration - (加速度)

Acceleration is defined as the rate of change of velocity with time . Acceleration is measured in meter per second second . (ms^-2) . Formula  (a= v-u/t)

=加速是定义为速度随时间的变化率。加速以每米一秒。

6. - Deceleration - (减速度)

Deceleration is defined as negative acceleration .

=减速被定义为负数的加速度。

*************************************************************************

(Ⅰ) An object is said to move with UNIFORM ACCELERATION if the rate of change of its velocity is constant .

=一个object，被称为''匀加速移动'' , 如果它速度的变化率是constant的。

(Ⅱ) An object is said to move with ZERO ACCELERATION if its velocity remains constant .

=一个object , 被称为是''零加速移动'' , 如果它的速度保持不变。

Ticker-Tape Timer (股票磁带计时器)

It is a narrow paper tape which can be passed through printing devices that place symbols ranging from simple dots to alpha-numeric symbols.

=这是一个狭窄的纸带可通过打印设备通过该地方的象征，从简单的点，以字母和数字符号

*Regardless of the type of recording timer used, the marks are made at regular time intervals.

=无论使用的类型的录音定时器，标记都是由定期的时间间隔而定。

*These time intervals are usually small fractions of second, and can be determined by comparing the number of dots made on a strip of paper tape as it is pulled through the timer to the number of seconds ellapsed (recorded by a stop watch) while the paper is being pulled.

= 这些时间间隔通常是第二小分数，并且可以通过比较以纸胶带条作出的点数，因为它是通过对经过的秒数（用秒表记录）而纸拉定计时器拉

a. Constant Speed or Velocity Examples: 

Ticker Tape: "Slower" speed

*   *   *   *   *   *   *   *   *  *  *  *  *  *  *  *  *  *  *

  
 

Ticker Tape: "Faster" speed

*         *         *          *         *         *         *         *           *           *            *            *             *         *

 

b. Acceleration, Increasing Speed or Velocity Examples:

Ticker Tape: "slower" acceleration

**  *    *       *           *                 *                       *                               *                                       *

  
 

Ticker Tape: "Faster" acceleration

**   *        *               *                        *                                   *                                       *

 

C. Deceleration, Decreasing Speed or Velocity Examples:

Ticker Tape: "slower" acceleration

**  *    *       *           *                 *                  *                   *                    *

  

  
 

Ticker Tape: "faster" deceleration

*                                          *                              *                   *           *      *   * *

* Each tick length then shows the distance covered in 0.2s and is therefore a measure of the average velocity during the time interval of 0.2s
=每个刻度的长度在0.2秒，然后显示所涉及的距离，因此时间间隔内的平均流速测量在0.2秒


* The four equation of linear motion are :
(i) V= u + at
(ii) V² = u² + 2as
(iii) s = ut + 1/2 at²
(iv) s = 1/2(u+v)t


Analysing Motion graphs (分析运动图)





** A car is travelling at constant speed
=汽车行驶在一个恒定速度





**A car is travelling with increasing velocity

=汽车是行驶速度增加

** A car is travelling with decreasing velocity

=汽车是行驶的速度递减

** A car is at rest (stationary)

=汽车是在休息（原地）

In a s-t graph, the velocity at any time is given by the slope of tangent to the graph at the instant. If the speed is uniform, the graph inclined straight line.

=在speed & time graph中，在任何时候给予的速度切线斜率在瞬间图。如果速度是均匀的，图形倾斜直线。

Speed - time graph ( v-t graph )
v-t graph gives the velocity of a moving object at different time. Here are 4 v-t graph representing the motion of 4 cars:
=一个移动的物体在不同时间的速度。这里有4个名词图代表了4辆汽车的议案


(a)



(b)



(c)



(d)



The acceleration at any time is given by the slope of tangent to the graph at that time
=在任何时候加

速度的切线斜率图

The area enclosed by the graph between a certain time interval represent the displacement of the car travelled during that time interval.

=在一定的时间间隔之间的封闭图形的面积代表在这段时间间隔行驶的汽车排量。

• ab : Object increases its velocity from rest. (Acceleration)
• =增加其速度。 （加速）
• bc : Object decreases its velocity to zero. (Deceleration)
• =降低它的速度为零。 （减速）
• cd: Object INCREASES its velocity from rest but it travel in REVERSE direction. (ACCELERATION)
• =增加其速度，但它在相反方向的走。 （加速）
• de: Object DECREASES its velocity to zero and it travel in REVERSE direction. (DECELERATION)
• =下降的速度为零，它在相反方向的走。 （减速）

Acceleration - time graph ( a-t graph )

Physics F4 Chapter 1

Understanding Physics ( 了解物理 )

Physics is study of the natural phenomena and the properties of matter .

=物理学是自然现象和物质的性质研究。

Understanding Base Quantities and Derived Quantities ( 理解基本的数量和派生量 )

1. A physical quantity is any quantity that can be measured by scientific instrument . 

= 任何一个物理量都可以用科学仪器来测量。

2. The value of the measurement consists of a magnitude and a unit .

=它是由magnitude和unit来测量value。

3. Other examples of physical quantities are Velocity (v) , Force (F) , and Time (t) .

=物理量的另一个例子是速度（V），力（F）和时间（t）。

4. A base quantity is a physical quantity which cannot be defined in terms of other physical quantities .

=一个基本的数量是一个物理量，不能在其他物理量的界定。

5.The five base quantities are length (m) , mass (kg) , time (s) , temperature (k) , and electric current (A) .

=这五个基地数量有：长度 (m) ，质量 (kg) ，时间(s) ，温度 (s) 和电流 (k) 

6. Examples of scientific instrument stopwatch , metre rule , balance thermometer , ammeter .

=科学仪器的例子：秒表，米尺，平衡温度计，电流表。

7. The International System of Units , known as SI , is based on the metric system of measurements .

=国际单位制，为 SI ，是一种基于测量的公制。

8. A derived quantity is a physical quantity which can be defined through multiplication , division or both these operations .

=派生的数量是一个物理量，可以通过乘法，除法或两者用来操作这些定义。

9. For easier recording and comparison , very large or very small measurement of physical quantities are represented by ''prefixes'' as shown in the table below.

=为了便于记录和比较，非常大或非常小的物理量测量为代表的叫做''前缀'' ，如下表所示。

Prefix	Symbol	Multiplication factor
yotta	Y		1024
zetta	Z		1021
exa	E		1018
peta	P		1015
tera	T		1012
giga	G	1 000 000 000	109
mega	M	1 000 000	106
kilo	k	1000	103
hecto	h	100	102
deka	da	10	101
deci	d	0.1	10-1
centi	c	0.01	10-2
milli	m	0.001	10-3
micro	µ	0.000 001	10-6
nano	n	0.000 000 001	10-9
pico	p		10-12
femto	f		10-15
atto	a		10-18
zepto	z		10-21
yocto	y		10-24

10. The prefixes are usually used to simplify the expression of very large or small number . 
=前缀通常用来简化非常大的或小的数目


11. The 11 derived quantities are area , volume , density , velocity , momentum , acceleration , force , pressure , weight , work and power .
=这11项派生数量有：面积，体积，密度，速度，动量，加速度，力，压力，重量，工作 和力量。


12. Scientific notation is the way that scientist easily handle very large numbers or very small numbers. 
=科学记数的方式是方便科学家们处理大量或非常小的数字


13. For example, instead of writing 0.0000000056, we write 5.6 x 10^-9. So, how does this work?
=例如，不要写成0.0000000056，我们写5.6 × 10-9. 那怎么做？


14. We can think of 5.6 x 10^-9 as the product of two numbers: 5.6 (the digit term) and 10^-9 (the exponential term).
=我们可以把5.6 × 10-9为两个数的乘积：5.6（该数字学期）及10-9（该指数项）。


15. Here are some examples of scientific notation.
=下面是科学记数法的一些例子。

10000 = 1 x 104	24327 = 2.4327 x 104
1000 = 1 x 103	7354 = 7.354 x 103
100 = 1 x 102	482 = 4.82 x 102
10 = 1 x 101	89 = 8.9 x 101 (not usually done)
1 = 100
1/10 = 0.1 = 1 x 10-1	0.32 = 3.2 x 10-1 (not usually done)
1/100 = 0.01 = 1 x 10-2	0.053 = 5.3 x 10-2
1/1000 = 0.001 = 1 x 10-3	0.0078 = 7.8 x 10-3
1/10000 = 0.0001 = 1 x 10-4	0.00044 = 4.4 x 10-4

16. In scientific notation, the digit term indicates the number of significant figures in the number.
=在科学记数法，长期的数字显示在有效数字位数的号码。

Understanding Scalar Quantities and Vector Quantities .( 了解标量和矢量量。)


1. Scalar quantity is a physical quantity which has magnitude or size only .
=标量是一个物理量的数量或大小而已。


2. The examples or scalar quantities include distance , speed , volume , temperature , and time .
=这些例子或标量，包括距离，速度，体积，温度和时间。


3. Vector quantity is a physical quantity which has direction as well as magnitude .
=矢量是一个物理量,有方向和大小。


Understanding Measurements (了解测量)


1 -Consistency- (一致性)
The consistency of a measuring instrument is the ability of the instrument to produce readings that are consistent with little or no variations in the different readings of the same physical quantity.
=一个测量仪器的一致性是仪器读数的能力的产生与在同一物理量的不同读数很少或根本没有变化相一致。


2. - Accuracy (准确性)
The accuracy of a measurement is the proximity of the measurement to actual value of the quantity measured .
=一个测量精度是测量距离量测到的实际价值


3. - Sensitivity - (灵敏度)
The sensitivity of an instrument is the ability of that instrument to detect small changes in the quantity being measured .
=对仪器的灵敏度是该仪器能够检测的数量被测量的微小变化。


4. - Systematic Errors - ( 系统误差 )
Systematic errors are errors caused by the condition of the measuring instrument or the state of the environment in which the measurement in which the measurement are taken .
=系统误差是由测量仪器的条件或在其中的测量中，测量采取的环境状况引起的错误。


5. - Zero Error - (零误差)
Zero error refers to error in instrument that do not show zero reading when its reading should be zero .
=零误差是指在仪器误差不显示零读数时，其读数应为零。


6. - Random Error - (随机误差)
Random error are error due to the experimenter's inability to take the same measurement in exactly the same way to get the exact same number .
=随机误差的错误是由于实验者的无力采取完全相同的方式来获得同样数量的相同精确测量。


7. - Parallax Error - (视差)
Parallax error is the error due to the incorrect positioning of the eye .
=视差是错误是由于眼睛不正确的定位。


8. - Experimental error - (实验误差)
Experimental error or uncertainly refers to the difference between measured value of a quantity and its actual value .
=实验误差或不确定性是指测量值之间的数量和其实际价值的差额。


Understanding Measuring Instrument (了解测量仪)


1. - Measuring Cylinder - (量筒)
The measuring cylinder is used to determine volume of liquid
=量筒用于确定液体的体积。


2. - Ammeter - (电表)
The ammeter is used to measure electric current .
=电流表是用来测量电流。


3. - Meter rule - (米尺)
The meter rule is used to determine the length accurately up to 0.1cm only . 
=米尺是用来确定准确的长度可达0.1公分而已


4. - Micrometer screw gauge - (螺纹千分尺规)
The micrometer screw gauge can be used to measure very small lengths such as the diameter of a wire or the thickness of a piece of paper as it can measure length accurately up to 0.01mm .
=螺纹千分尺测量，可用于测量非常小的长度，如金属线的直径或一张纸，因为它可以精确地测量长度可达0.01mm的厚度。


5. - Vernier Calipers - (游标卡尺)
Vernier Calipers can measure length with an accuracy of up to 0.01cm . 
=游标卡尺可以测量的准确度到0.01厘米


6. - Stopwatch - ( 秒表 )
The analogue stopwatch measures time in intervals of 0.1s .
=秒表测量时间的模拟在0.1秒的间隔


7. - Digital Stopwatch - (电子秒表)
The digital stopwatch measures time in intervals of 0.001s .
=秒表测量时间的模拟在0.01秒的间隔


8. - Triple beam balance - ( 三重平衡梁 )
A triple beam balance can measure the mass of an object with an accuracy of 0.1g .
=一个三重平衡可以测量0.1克的物体的质量的精度。


* Ammeter and milliammeters must be connected in series in an electrical circuit because these meters have very low resistance .
=电流表和milliammeters必须连接在一个电路，因为这些meters，具有非常低的电阻串联。


- END FROM CHAPTER 1 -