Physics Spm Chapter 1 Form 4

LEARNING OBJECTIVES

By the end of this lesson you should be able to:

1. Understanding physics

* Explain what Physics is * Recognize the Physics in everyday situations and natural phenomena

1.2 Understanding Base quantities and derived quantities

* Explain what base quantities and derived quantities are * List base quantities and yheir units * List derived quantities and their units * Express quantities using prefixes * Express quantities using scientific notation * Express derived quantities as well as their units in terms of base quantities and base units * Solve problems involving conversion of units

1.3 Understanding scalar and vector quantities * Define scalar and vector quantities * Give examples of scalar and vector quantities

1.4 Measuring Physical quantities

* Measure physical quantities using appropriate instruments * Explain accuracy, consistency and sensitivity * Explain types of experimental errors * Use appropriate techniques to reduce errors * Use the vernier calipers and micrometer screw gauge

1.5 Analyzing a scientific investigations

* Identify variables in a given situation * Identify a question suitable for scientific investigation * Form a hypothesis * Design and carry out a simple experiment to test the hypothesis * Record and present data in a suitable form * Interpret data to draw a conclusion * Write a report of the investigation.

CHAPTER 1: INTRODUCTION TO PHYSICS

1.1 Understanding Physics

1. Physics is the branch of science concerned with the study of natural phenomena and properties of matter and energy.

2. Name several physics concepts related to daily live or natural phenomenon.

Choose from the list below : Surface tension Refraction of light Friction Inertia Resonance Air resistance Density Gravitational force / radio wave Reflection of light

|No. |Phenomena |Physics concepts |
|1 |A straight stick seems bent in water. |Refraction of light |
|2 |Satellites do not fall out of the sky. |Gravitational force |
|3 |While a car is braking to a stop, you continue in motion, sliding along |Inertia |
| |the seat in forward motion. | |
|4 |More massive object (a stone) falls faster than less massive object (a |Air resistance |
| |feather). | |
|5 |People can communicate using mobile phones. |Electromagnetic wave// radio wave |
|6 |We can see the image of an object in a mirror. |Reflection of light |
|7 |A submarine can sail on the sea surface and under the sea. |Density // Upthrust |
|8 |We can walk on a floor without falling. |Friction |
|9 |A singer can scatter a glass by singing a certain note. |Resonance |
|10 |A needle can be made to float on a surface of water. |Surface tension |

3. Fields of study in Physics.
|No. |Field of study |Explanation |
|1 |Force and motion/ Mechanics |Investigates the action of force and motion. |
|2 |Heat |Studies of heat on different types of matter. |
|3 |Light / Optics |Explain the different phenomena due to light and sight. |
|4 |Waves |Understanding the properties of different types of waves and |
| | |their users. |
|5 |Electricity and electromagnetism |Investigate the interaction of electric and magnetic fields. |
|6 |Electronics |Studies the use of electronics devices in various fields. |
|7 |Nuclear physics |Study of nuclear structure and their application. |

4. Importance of physics (a) There is a close relationship between the study of physics and other sciences, including astronomy, biology, chemistry and geology.

(b) There is a close connection between physics and the practical developments in engineering, medicine and technology .

(c) The application of fundamental laws and theories have enabled engineers and scientists to put satellites into orbit, receive information from space probes, and improve telecommunications.

(d) Physics improves the quality of life, i.e. many home appliances function through the operation of principles of physics .

2. Understanding base quantities and derived quantities.

1. A physical quantity is a quantity that can be measured. The value of the measurement consists of a numerical magnitude and a unit. Example: 1. A book with a mass of 2 kg Physical quantity : mass Numerical magnitude/value: 2 Unit of measurement (SI unit) : kg

2. Length of a meter rule is 100 cm Physical quantity : length Numerical magnitude/value: 100 Unit of measurement (SI unit) : cm

3. Temperature of boiling water is 100 oC Physical quantity : Temperature Numerical magnitude/value: 100 Unit of measurement (SI unit) : oC

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

2. Other examples of physical quantities are velocity, force and time.

3. All physical quantities can be classified into two groups : a) A base quantity is a physical quantity that cannot be defined in terms of other physical quantities. A table below shows five base quantities and their respective SI units.

|Base quantity |Quantity symbol |SI unit |Symbol |
|Length |l |metre |m |
|Mass |m |kilogram |kg |
|Time |t |second |s |
|Electric current |I |ampere |A |
|Temperature |T |kelvin |K |

b) A derived quantity is a physical quantity which is obtained by combining base quantities by multiplication, division or both these operations

|Derived quantity |Relationship with the base quantities |Relationship with the |Derived units |
| | |units | |
|Volume, V |Length x breadth x height |m x m x m |m3 |
|Density, ρ | [pic] |[pic] |kg m-3 |
|Velocity, v |[pic] |[pic] |m s-1 |
|Acceleration, a |[pic] |[pic] |m s-2 |
|Momentum |Mass x Velocity |kg x m s-1- |kg m s-1 |
|Force, F |Mass x Acceleration |kg x m s-2 |kg m s-2 (N) |
|Impulse |Change of momentum |kg x m s-1 |kg m s-1 (Ns) |
|Energy, E |Force x Displacement |kg m s-2 x m |kg m2 s-2 (J) |
|Power, P |[pic] |[pic] |kg m2 s-3 (W) |

4. A value in standard form or scientific notation is a value written in the form of

where 1 [pic] A < 10 n is an integer (….,-2, -1, 0, 1, 2, ….)

Example :

| |Value |Value in standard form |
|The size of a flu virus |0.000 000 2 m |2.0 x 10-7 m |
|The equatorial diameter of earth |12 760 000 m |1.276 x 107 m |

5. We use prefixes to simplify the expression of very big or very small numerical values of physical quantities. A Prefix is a multiplying factor used to present large or small value 6.
| Prefix |Symbol |Value |
|tera |T |x 1012 |
|giga |G |x 109 |
|mega |M |x 106 |
|kilo |k |x 103 |
|deci |d |x 10-1 |
|centi |c |x 10-2 |
|mili |m |x 10-3 |
|micro |μ |x 10-6 |
|nano |n |x 10-9 |
|pico |p |x 10-12 |

7. Conversion of units

Example : Convert to SI unit and standard form.

a) 3.4 km = 3.4 x 103 m = 3400 m

b) 1.5 g cm-3 = [pic] = [pic] = 1.5 x 10 3 kg m-3 c) 72 km h-1 = [pic] = [pic] = 20 ms-1

7. Solve problems that involve the conversion of units. Complete the table below with standard form and convert the unit

|Quantity |Standard form |Convert to unit |
| |Scientific notation | |
|1) 0.000 000 18 Ts |1.8 x 10-7 Ts | (1.8 x 10-7 x 1012 )-(-6) |
| | |= 1.8 x 10-7 x 1018 |
| | |= 1.8 x 1011 μs |
| | | |
| | | |
| | |(μs) |
|2) 0.2341 mg |2.34 x 10-1 mg | ( 2.34 x 10-1)x 10 -3-(-6) |
| | |= 2.34 x 10-1)x 10 -9 |
| | |= 2.34 x 10-10 Mg |
| | | |
| | | |
| | | |
| | |(Mg) |
|3) 3 854 000 Gm |3.854 x 106 Gm | (3.854 x 106) x !09-3 |
| | |= 3.854 x 106 x !06 |
| | |= 3.854 x 1012 km |
| | | |
| | | |
| | | |
| | |(km) |
|4) 7 530 nA |7.530 x 103 nA | (7.350 x 10 3 ) x 10 -9-(3) |
| | |= 7.350 x 10 3 x 10 -6 |
| | |= 7.350 x 10 -3 mA |
| | | |
| | | |
| | | |
| | | |
| | |(mA) |
|5) 5 K |5 x 100 K | 5 x 100 x 100 – (-12) |
| | |= 5 x 1012 pK |
| | | |
| | | |
| | | |
| | |(pK) |

3. Understanding scalar and vector quantities

1. Physical quantities can be classified as scalar quantities and vector quantities. a) A scalar quantity is a physical quantity which has magnitude only. Examples : time, length and current b) A vector quantity is a physical quantity which has both magnitude and direction. Example : Force and velocity

2. Complete the table by choosing the correct physical quantities from the list below.

Length Displacement Velocity Density Force Current Acceleration Temperature Momentum Work Weight Time Distance Speed Energy Depth Area Volume Mass Power

| Scalar quantities |Vector quantities |
| Length Time | Displacement |
|Area Volume |Velocity |
|Distance Speed |Force |
|Work Energy |Acceleration |
|Temperature Density |Momentum |
|Mass Current |Weight |
|Depth Power | |

4. Using appropriate instruments to measure

Recognizing appropriate instruments for measuring.

Choose the appropriate tools to match with the picture given.

Stop watch Micrometer screw gauge Metre rule Ammeter Vernier callipers Waist watch Measuring tape Triple beam balance Thermometer

|Object |Measuring Tools |
| | |
|Temperature of |Thermometer |
|boiling water | |
| | |
|Running Time | |
| |Stop watch |
| | |
|Book thickness | |
| |Vernier callipers |
| | |
|Electric current | |
| |Ammeter |
| | |
|Diameter of a wire | |
| |Micrometer screw gauge |
| | |
|Mass of a key | |
|( |Triple beam balance |

1.4.1 Accuracy

1. Accuracy of a measurement is how close the value of a measurement to the actual value.

2. The level of accuracy is related to the relative error.

3. Relative error = [pic] x 100 %

4. An error is a difference between the measured value and the actual value or true value .

5. Accuracy can be improved by : -

(a) repeated readings are taken and the average value is calculated (b) avoid parallax errors (c) avoid zero errors (d) use measuring instruments with a higher accuracy. For example, a vernier callipers is more accurate than a ruler .

1.4.2 Consistency

1. Consistency / Precision is the degree of an instrument to record consistent readings for each measurement by the same way or the ability to record the same readings when a measurement is repeated.

2. A measurement is considered consistent will have a small relative deviation or no deviation from the average value .

3.. A deviation is a difference between a measurement value and its average value .

4. average deviation = [pic]

5. relative deviation = [pic] x 100 %

Example: A student used vernier callipers to measure diameter of a glass rod. The table below shows the readings.
|Measurement |Diameter rod (cm) |Deviation |
|1 |2.23 |0.01 |
|2 |2.26 |0.02 |
|3 |2.24 |0.00 |
|4 |2.23 |0.02 |
|5 |2.25 |0.01 |
|Average |2.24 |0.012 |

Relative deviation = [pic]

= 0.54 %

6. Consistency can be improved by

(a) eliminating parallax errors (b) exercising greater care and effort when taking readings. (c) using an instrument which is not defective.

7. Comparisons between consistency and accuracy

a) Consistent but not accurate b) Accurate but not consistent

c) Accurate and consistent d) Not accurate and not consistent.

1.4.3 Sensitivity

1. Sensitivity of an instrument is its ability to detect a small change in the quantity to be measured.

2. A measuring instrument that has a scale with a smaller divisions is more sensitive .

3. Measuring instruments.

|Measuring instruments |Smallest magnitude of quantity |Sensitivity / Accuracy |
| |(cm) | |
|Metre rule |0.1 |0.1 cm (low) |
|Vernier callipers |0.01 |0.01 cm (moderate) |
|Micrometre screw gauge |0.001 |0.001 cm (high) |

1.4.4 Experimental Error

1. An error is a difference between the true value of a quantity and the value obtained in measurement .

2. There are two main types of errors : (a) systematic errors (b) random errors

3. Systematic errors - The error in calibration of instrument which makes the instrument defective. (We must examine the instrument carefully before using them)

- Zero error which means the pointer of the instrument does not return to zero when not in use. ( Zero error can be corrected by compensating the readings)

- A problem which persists throughout the experiment such as repeated error in reaction time and wrong assumption.

- Systematic errors will lead to decrease in accuracy

4. Random errors - arise from unknown and unpredictable variations in condition, and will produce a different error every time you repeat the experiment. - may be due to: (a) personal error ( human limitations of sight and touch ) (b) lack of sensitivity ( instrument does not respond / indicate insignificant or small change ) c) natural errors ( wind , temperature, humidity, refraction, magnetic field or gravity ) (d) wrong technique ( applying excessive pressure when turning a micrometer screw gauge ) - can be minimized by repeating the measurement several times and taking the average (mean) of the reading .

5. Parallax error - An error in reading a measurement because an observer’s eye and the pointer are not in a line perpendicular to the plane of the scale .

(We should place our eyes directly perpendicular in front of the pointer or scale of an instrument when taking measurements )

[pic] [pic]

. 1.4.5 Measurement of length

|Instrument |Example |
|Measuring tape |To measure a waist of a man. |
|Metre rule |To measure the length of a table |
|Vernier callipers |To measure thickness of text book |
|Micrometre screw gauge |To measure a diameter of a glass rod or wire |

A. Metre rule To measure length from a few cm up to 1 m.

1. Precautions to be taken when using a ruler: (a) ensure that the object is in contact with the ruler to avoid inaccurate readings. (b) avoid parallax errors (c) avoid zero error and end error.

2. For example: A ruler is to determine the diameter of the wire.

[pic] Solution: Length of wire Diameter of wire, d = ---------------------------- No. of coils 1.5 - 1.0 = ------------------- 10 = 0.05 cm

B. Vernier callipers

1. Two pairs of jaws (a) outside jaws: to measure linear dimensions and outer diameters (b) inside jaws : to measure inner diameters

2. Two steel bar scales (a) the main scale (b) the vernier scale - has a scale on which ten divisions are equal to nine small divisions on the main scale . [pic]

3. Errors in the vernier callipers (a) No zero error [pic] (b) Positive zero error [pic] Positive zero error = + 0.04 cm

(c) Negative zero error [pic] Negative zero error = - ( 1.0 - 0.08 ) = - 0.02 cm

4. For example: Figure below shows the use of a vernier callipers to measure the size of spherical object. Determine the correct size of the object if the zero error of the vernier callipers is (a) - 0.08 cm (b) + 0.08 cm Example 1 : [pic]

(a) Zero error = - 0.08 cm Main scale reading = 2.10 cm Vernier scale reading = 0.05 cm Vernier caliper reading = 2 . 1 + 0.05 = 2.15 cm Correct size of object = vernier caliper reading - zero reading = 2.15 - ( -0.08 ) = 2.23 cm

(b) Correct size of object = 2.15 - ( +0.08 ) = 2. 07 cm

Example 2 : [pic]

(a) Zero error = -0.08 cm

Main scale reading = 3.70 cm Vernier scale reading = 0.04 cm Vernier caliper reading = 3.74 cm Correct size of object = vernier caliper reading - zero reading = 3.74 – (-0.08 ) = 3.82 cm

(b) Correct size of object = 3.74 – 0.08 = 3.66 cm C. Micrometer Screw Gauge

1. Comprises of (a) main scale on the sleeve (b) thimble scale on the thimble

[pic]

2. Errors in micrometer screw gauge (a) No zero error [pic]

(b) Positive zero error [pic]

Correct reading = micrometer reading - ( 0.04 )

c) Negative zero error [pic] Correct reading = micrometer - ( -0.03 ) Figure below shows a micrometer screw gauge used to measure the size of an object. Determine the size of the object if the micrometer has a zero error of (a) + 0.01 mm b) - 0.03 mm

Example 1 :

[pic] Solution : The main scale reading = 4.50 mm The thimble scale reading = 0.21 mm The reading of the gauge = 4.50 + 0.21 = 4.71 mm

(a) Size of object = the reading of the gauge - zero error = 4.71 - 0.01 = 4.70 mm

(b) Size of object = 4.71 - ( - 0.03 ) = 4.74 mm

Example 2 : [pic]

Solution : The main scale reading = 1.00 mm The thimble scale reading = 0.37 mm The reading of the gauge = 1.37 mm

(a) Size of object = the reading of the gauge - zero error = 1.37 – 0.01 = 1.36 mm

(b) Size of object = 1.37 – (-0.03) = 1.40 mm 1.4.6 Measurement of time 1. Stop watches are used to measure time interval .

2. Two types of stop watches (a) The analogue stop watch which is mechanically operated (b) The digital stop watch which is electronically operated.

1.4.7 Measurement of mass The mass of an object can be measured using a beam balance or an electronic balance .

1.4.8 Measurement of temperature 1. A thermometer is an instrument used to measure temperature

2. Types of thermometer (a) clinical thermometer (b) mercury thermometer (range – 100C to 1100C with an accuracy of 10C ) (c) mercury thermometer (range 0 0C to 360 0C with an accuracy of 2 0C )

3. A mercury thermometer is a sensitive instrument because : - (a) Mercury is a liquid metal which is sensitive to temperature changes. It expands and contracts uniformly with the temperature . (b) The thin – walled glass bulb allows a quick heat transfer between the heat source and the mercury (c) The capillary tube , which has a small diameter , amplifies a small expansion in the bulb into a large linear expansion along the length of the capillary tube .

1.4.9 Measurement of electric current and voltage

Ammeter 1. An instrument used to measure the amount of electric current flowing through a particular point in an electrical circuit .

2. The SI unit for current is Ampere, A

3. For a small current , a milliammeter is used ( an accuracy of 0.1 mA or 0.2 mA is used )

4. It is usually connected in series in an electrical circuit .

Voltmeter 1. An instrument used to measure the potential difference ( voltage ) between any two points in an electrical circuit 2. The SI unit for potential difference is volt, V.

3. It is connected in parallel in an electrical circuit . [pic]

1.5 Analysing scientific investigations 1. The following processes are involved in scientific investigations.

a) A scientific investigation begins with observation. When observing we come out some questions.. (i.e : hearing, smelling, touching, tasting, seeing)

b) Making inference is a early assessment or explanation that is carried out to answer the question raised. Inference is an early conclusion to what we observed

b) Form a hypothesis which is the statement of relationship between the manipulated variable and the responding variable we would expect.

c) Aim has to be stated so that all the investigating effort is centred on the main subject.

d) Identify all the variables ; i ) Manipulated variable is a quantity we manipulate / variable which causes other secondary variables to change. ii) Responding variable is the quantity which is affected by the manipulated variable and is measured experimentally. iii) Fixed variable is the quantity that does not change throughout the experiment.

e) Apparatus / Materials needed to be listed according its specification example measuring instrument to ensure the success the experiment.

f) Procedure is the sequence of action or operation in order to carry out the experiment according to the instructions given.

g) Observation is the listing and tabulation of all data obtained in the experiment.

h) Analysing of data can be carried out by plotting the graph, followed by the interpretation of graph or calculation to obtain the required value.

i) Discussion needs to be stated to find out whether the result obtained support the stated hypothesis. Precautions of the experiment can be suggested to overcome the weakness, to reduce the experimental error or to improve the result of the experiment.

j) A conclusion is stated concerning the result of the experiment (is written in accordance with the aim of the experiment and based on graph). By comparing with the aim stated, this will determine whether the hypothesis is accepted or rejected.

2. Example : A simple pendulum

1. Inference : When the length of a simple pendulum increases, the period of oscillation also increases. // The period of pendulum is affected by the length of the thread.

2. Hypothesis : The longer the length of a simple pendulum, the longer will be the period of oscillation//

3. Aim : To find the relationship between the length of a simple pendulum and the period of oscillation. 4. Variable : a) Manipulated variable : Length, l b) Responding variable : Period, T. c) Fixed variable : Mass of pendulum bob. m

5. Materials : Retort stand, pendulum bob, thread, metre rule, stop watch.

6. Figure

[pic] 7. Procedure : a) Set up the apparatus as shown in Figure above.// A small brass or bob was attached to the thread. The thread was held by a clamp of a the retort stand.

b) The length of the thread , l was measured by a metre rule, starting with 90.0 cm. The bob of the pendulum was displaced and released.

c) The time for 20 complete oscillations, t was taken using the stop watch. Calculate the period of oscillation by using, T = [pic] d) The experiment was repeated using different lengths such as 80.0 cm. 70.0 cm, 60.0 cm, 50.0 cm and 40.0 cm.

8. Observation / Tabulate data

|Length of string, l / cm |Time taken for 10 |Period of |T2 |
| |oscillation, t (s) |oscillation |(s2 ) |
| | |T =[pic](s) | |
| | t 1 | t 2 |Average, t | | |
|40.0 |25.2 |25.1 |25.2 |1.26 |1.59 |
|50.0 |28.1 |28.2 |28.2 |1.41 |1.99 |
|60.0 |31.0 |31.0 |31.0 |1.55 |2.40 |
|70.0 |33.5 |33.6 |33.6 |1.68 |2.82 |
|80.0 |35.7 |35.9 |35.8 |1.79 |3.20 |
|90.0 |38.2 |37.9 |38.1 |1.91 |3.65 |

Notes :

• Symbols and their respective units should be written in the table

• A readings of length of string should be written in one decimal place This is because the metre rule used to measure the length of string can measure accuracy to 0.1 cm

• All sets of readings recorded must be consistent. For example, all reading time taken, t are recorded in one decimal place.

• Average values for t are taken to minimize errors

• If the time taken for 20 oscillations is 38.1 s, Then the period of oscillation, T = [pic] = [pic] = 1.91 s T2 = (1.91)2 = 3.65 s2

9. Analysing : Plotting the graph

[pic]

Notes :

a) Plotting the graph

• The graph should be labeled by a heading

• All axes should be labeled with quantities and their respective units.

• The manipulated variable (l) should be plotted on the x-axis while the responding variable (T2 ) should be plotted on the y-axis

• Odd scales such as 1:3, 1:7 , 1:9 0r 1 :11should avoided in plotting graph.

• Make sure that the transference of data from the table to the graph is accurate.

• Draw the best straight line - the line that passes through most of the points plotted such that is balanced by the number of points above and below the straight line.

• make sure that the size of the graph is large enough, which is, not less than half the size of the graph paper or.( > 8 cm x 10 cm )

b) Calculate the gradient

• The triangle drawn to calculate the gradient of the graph should not be less than half size of the graph drawn or ( .> 6 cm x 8 cm ) • Calculate the gradient using the formula • Put the unit

10. Discussion / Precaution of the experiment / to improve the accuracy

a) The bob of the pendulum was displaced with a small angle b) The amplitude of the oscillation of a simple pendulum is small. c) The simple pendulum oscillate in a vertical plane only. d) Switch off the fan to reduce the air resistance

11. Conclusion

The length of simple pendulum is directly proportional to the square of the period of oscillation. //

T2 is directly proportional to l (the straight line graph passing through the origin)

-----------------------
Notes :
1 g = 10-3 kg
1 m3 = 106 cm3
1000 g = 1 kg
1 cm3 = 10-6 m3

Notes :
1 hour = 36000 s
1000 m = 1 km

A x 10 n

bob

thread

Retort stand T2 (s2) against l (cm)

T2
(s2 )

l (cm)

xx

x

x

x

x