Physics

Front 1

Methods of Telling/Measuring the Time

Back 1

All depends on some regular event. They can either be natural or devised.

Front 2

Rotation around the Sun

Back 2

It provides humans with a natural clock that counts in years as the Earth travels in orbit around the sun.

Front 3

The Sunidal

Back 3

A devised method of telling of the time is the Sundial. It divided up the day using the sun cast shadow of a rod as a slowly moving pointer across the dial.

Front 4

Automatic Clock

Back 4

We now use an automatic clock to give us an unvarying time which other clocks are checked.

The automatic clock chosen is the CAESIUM-133 atom.

Front 5

Period (T) of a Pendulum

Back 5

Front 6

The Simple Pendulum

Back 6

The simple Pendulum consists of a piece of thread that is fixed at one end and has a small metal ball called the BOB at the other end.

Hint 6

Front 7

The Swing of The BOB

Back 7

Front 8

The Periodic Time of The Pendulum

Back 8

The periodic time (T) of the Pendulum is the time taken for a complete swing or oscillation forwards and backwards from A to B to A to C.

Front 9

The length of the pendulum (L) is the distance from the point of support to the BOB.

Back 9

The amplitude of a swing is the angle between the extreme and rest positions of the thread.

Front 10

Factors which affect the period of a simple pendulum.

Back 10

1. Length of thread

2. Mass of pendulum Bob

3. Initial angle of displacement.

Front 11

Area

Back 11

Is the extent or measurement of a surface.

Area of a rectangle: length × breadth

Area of triangle: half × base × height

Area of disk: Pi × radius square

Area of a sphere: 4 × Pi × radius square.

The S.I unit of Area is square meters.

Front 12

Area can also be measured in centimeters square.

Back 12

The radius is the line from the center to the perimeter.

The diameter is any straight line that passes through the center of a circle whose end point lies on the circle.

Radius: d×2

Diameter: 2×radius.

Front 13

Temperature

Back 13

The 2 types of scales are:

Kelvin scale- k

Celsius scale- C°

The lowest point on the Kelvin scale is absolute 0. At 0°k molecules have zero thermal energy and can't become any colder. A temperature scale expresses how hot or cold something is.

Hint 13

Front 14

Volume

Back 14

The volume is the amount of space an object occupies.

The S.I unit of volume is cubic meters.

As cubic meter is rather large and gives high values of density we often can use cubic cm.

Hint 14

Front 15

Volume of rectangular blocks, cylinders and spheres.

Back 15

Rectangular block: length×breadth×height

Cylinder: height×Pi×radius cube

Sphere:4/3×Pi×Radius cube.

Front 16

Volume of Irregular Solids

Back 16

This can be measured by displacing the water in a measuring cylinder.

Hint 16

Front 17

Displacement Can

Back 17

Front 18

Volume of liquids.

Back 18

Measuring cylinder is used for large and small volumes.

It is less accurate than a burette.

The scale is read upward at the bottom of the meniscus at eye level.

The burette is more accurate than other instruments however the scale is read downwards.

Front 19

Graduated / Fixed

Back 19

The pipette can be either graduated or fixed.

With all these instruments the measuring must be upright and at eye level.

1 litre= 1000cm cube

1 milliliter = 1cm cube

Front 20

Instruments and Scales

Back 20

Instruments are used to measure quantity. These instruments are calibrated that is, they have a scale marked on them i the correct unit.

Sensitivity: a sensitive instrument responds to small changes in the quantity being measured.

Range: area of variation between upper and lower limits on a particular scale.

It is the max / min value an instrument can measure.

Front 21

Accuracy

Back 21

An accurate instrument gives the correct readings.

Linear scale- scale markings are evenly distributed.

Non-Linear: scale markings are not evenly distributed. It is difficult to estimate readings on Non linear scales.

Front 22

Error in instruments.

Back 22

They may be because of:

Apparatus: scale may be incorrectly calibrated.

Experimental condition: quantity (temperature varying when it should be constant)

The experimenter- when an estimate has to be made of a reading, between 2 marks on a scale.

Front 23

Random / Systematic Error

Back 23

Random Error: an unpredictable error where it takes an incorrect reading.

Systematic errors are usually results of a flaw in the measuring device or measurement technique may even be difficult to spot and may even be dangerous.

Front 24

Systematic error causes:

Back 24

An instrument that has an incorrect zero setting.

Incorrectly calibrated.

Measuring equipment changes quantity being measured.

Reading the instrument from incorrect position introduces a parallax error.

Front 25

Random error causes:

Back 25

The readings are scattered around the true value.

Random errors occur because the quantity measured may not be uniformed.

Where a human response factor is involved.

Front 26

Avoiding Errors

Back 26

Read instruments correctly, avoiding parallax error.

Use more than 1 technique to measure the same quantity.

Check instruments by substituting other ones for the same measurements.

Check instruments by looking for errors.

Front 27

Density

Back 27

Density of a substance is defined as its mass per unit volume.

The Greek letter 'P' (rho) is the symbol used for density but 'd' is also used.

The unit of density in S.I is kg/m cube.

Front 28

Density

Back 28

It tells us about how the matter in a substance.

Pure water has exactly the same density in a cup or in a pool.

It only changes if something else such as salt is in the water or if it is heated or cooled.

Front 29

Simple Density Measurements:

Back 29

Density = m ÷ v

1) Regular Shaped Solid:

The mass is found on a balanced scale.

The volume is found by measuring the length, breadth and height using a ruler, micro-meter screw gauge or vernier callipers depending on the size.

Front 30

Irregular Shaped Solid

Back 30

The solid is weighed and its volume measured by the displacement method.

Front 31

Liquids:

Back 31

A known volume is transferred from a measuring cylinder, burette or pipette, into a weighed beaker and reweighed to give the mass of the liquid.

Front 32

Air:

Back 32

A 500cm cube round bottomed flask is weighed full of air on a sensitive scale balance.

The air is then removed with s vacuum pump, the difference gives the mass of air in the flask.

The volume of air in the flask with water and pouring it into a measuring cylinder.

Front 33

Relative density:

Back 33

The relative density (Pr) tells you how many time a substance is denser than water.

Relative density = density of substance ÷ density of water (1g/cm cube)

Relative density has no units..