1.5 Understanding Scientific Investigations

1.5 Understanding Scientific Investigations


1. Scientific investigations are carried out systematically.

2. If a certain scientist obtains a certain result doing an experiment, any other scientist doing the same experiment will obtain the same result if the procedure is carried out in the same systematic way.

3 The scientific investigation process follows the following sequence:
• Identification of the problem
• Identification of the variables of the experiment
• Formulation of a hypothesis
• Design of the experiment
• Establishing the procedures of the experiment
• Collection of measurement data and tabulation
• Analysis of the data
• Deriving a conclusion

1.4 Understanding Measurements

1.4 Understanding Measurements

1. Sensitivity of an instrument is a measure of how small a change in the measured quantity the instrument can detect.Precision of a measurement is a measure of the consistency of the readings obtained when the quantity is measured repeatedly.Accuracy of a measurement is a measure of the closeness of the measured value to the actual value of the quantity measured.

2. All measurements have a certain amount of uncertainty. The amount of uncertainty is also known as the error in the measurement. Error does not mean mistake. It just refers to the uncertainty in a measurement.

3. Errors can be caused by

(i) the limitation due to the smallest division in the scale of the measuring instrument.

The uncertainty (error) of ±0.1 is due to the smallest division of the scale being 0.1 cm.

(ii) random errors

Random errors are caused by

• the inability of the experimenter to be consistent in repeating the measurement (this is known as personal errors)

• the non-uniformity in the measured quantity (example the diameter of a wire may be non-uniform)

• disturbances due to unstable external conditions (example, there may be wind that makes it difficult to record the measurement)In order to minimize this error, a measurement is repeated many times and an average value istaken.

4. Systematic errors are caused by

• defects in the instruments

(For example, when the magnitude of the measured quantity is zero, the pointer of the instrument may not coincide exactly with the zero mark on the scale. This is known as a zero error.)

• defects in the procedure of the experiment

Systematic errors are handled by making a correction to the measured quantity if the actual difference due to the systematic error is known.

For example, if the reading of a ruler is 4.8 cm and the zero error is —0.2 cm, then the reading is corrected by subtracting the zero error from the measuredvalue.

5. Random errors lead to a decrease in precision of the measurement.Systematic errors lead to a decrease in the accuracyof the measurement.

4.8 — (—0.2) = 5.0 cm

6. The vernier caliper is a length measuring instrument that is more sensitive than the ruler. The smallest change that can be detected with a ruler is 0.1 cm while the smallest change that can be detected with vernier caliper is 0.01 cm (0.1 mm).

7. The micrometer screw gauge is more sensitive than the vernier caliper. The smallest change that can be detected with a micrometer is 0.001 cm (0.01 mm).

1.3 Understanding Scalar and Vector Quantities

1.3 Understanding Scalar and Vector Quantities





1. Scalar quantities are quantities which have magnitude only.





Examples of scalar quantities are mass, time, temperature, electric current, speed, volume, density, pressure, energy, power.





2. Vector quantities are quantities which have magnitude and direction.





Examples of vector quantities are displacement, velocity, acceleration, momentum, force.





3. Scalar quantities are added and subtracted in the same way as ordinary numbers are added and subtracted.





Example: 5 kg — 3 kg = 2 kg





4. Vector quantities are added and subtracted using parallelogram of vectors or triangle of vectors.





Example: A 3 N force is inclined at an angle of 30 degree to a 5 N force. They are added as follows:

The lengths of the arrows represent the magnitudes and
the directions of the arrows represent the directions of the forces respectively.

1.2 Understanding Base and Derived Quantities

1.2 Understanding Base and Derived Quantities

1. A physical quantity is a property of nature. It can be in relation to phenomena, objects or substances. Examples of physical quantities are:

(i) energy of a radiation — energy is the quantity relating to the phenomenon of radiation

(ii) length of a field — length is the quantity relating to the object which is the field

(iii) density of a liquid — density is the quantity relating to the substance which is the liquid.

2. Scientific notation is used for expressing very large and very small numbers.

Example:

>3800 m = 3.8 x m

>0.000456 s= 4.56 x 10 s

3. Powers of ten can be expressed in terms of multiple and sub-multiple prefixes as shown below:

4. All physical quantities are associated with a magnitude, which is the number expressing the size of the physical quantity, and most of the physical quantities are associated with a unit.

For example, in the statement “50 metres’ ‘50’ is the magnitude and ‘metre’ is the unit.

5. SI units are a set of units agreed upon internationally by the 11th General Conference on Weights and Measures held in 1960.

6 Base quantities are a set of quantities which are independent of one another and any one of them cannot be expressed in terms of a combination of the others.

7 The five base quantities, their symbols, the corresponding SI units and symbols are:

8. Derived quantities are a combination by multiplication or division of one or more base quantities.

1.1 Introduction to Physics

1.1 Understanding Physics

1. Physics is the study of matter, energy and the relationships between them.

2. In Physics, we make observations of natural phenomena, record them and make connections between the various observed phenomena.

3. By this process, the many different phenomena are organized into a few fundamental laws of physics.

4. Thus, new processes can be predicted and new gadgets can be invented based on the physical laws.

5. Technology is based on physics laws and through technology, many appliances are invented which make our lives more convenient.