Length, volume, density and time

Measuring with a rule

• The object to be measured must be straight and laid close to the rule
• Look at the ends of the object whether they are straight
• Look at the markings on the rule and line one end against the 0, then read the scale at the other end of the object.
• The length can be determined within a milimetre
• How the rule is made is what should be thought about; whether the rule is correctly calibrated or not ^{(are the markings separated by exactly one metre?})

Other measurement techniques

• For small or thin lengths, measure many of them then divide it by the amount of the object collected.
• For measurements like curved lines and circumferences, put a thread on it then mark the ends on the thread. Later, lay it on a rule
• A micrometer screw gauge is used to measure very small distances. It has 2 scales, the main scale on the shaft and the fractional scale on the rotating barrel.The fractional scale has 50 divisions and one turn represents 0.50 mm.
• Turn the barrel until the jaws tighten on the object and use the friction clutch so it is well pressured. Read the main scale to the nearest 0.5 mm and the additional fraction of a milimetre from the fractional scale. Then add the two

Measuring volume

• Regularly shaped objects: Measure the lengths and multiply them together. For shapes such as spheres and cylinders, measure according to the formula for the volume
  
• Liquids: Use measuring cylinders with its scale being double the volume.
• Irregular shaped objects: The technique is measuring volume by displacement. Select a cylinder 3 or 4 times bigger than the object, fill it with enough water to cover the object, then write down the scale. Then put in the object and note down the increase in volume, for it is the volume of the object

• Formula: density (ρ) = mass (M) / volume (V); the ratio of mass to volume for a substance
• SI unit is kg/m³. The density of water is 1000 kg/m³

Measuring density

•  Liquid: Place the measuring cylinder on a balance, then set it to 0 and pour liquid. Read the scale of the cylinder for the volume and the balance for the mass
• Irregular shaped object: The method of displacement is to first partly fill a cylinder with water and note its volume then submerge the object into the water and note the volume. Then calculate its density as usual

Measuring time

• Analogue clock: Find the by looking at where the hands are pointing
• Digital clock: The time is written in numerals
• Light gate: It is used to study motion. It is connected to an electronic timer
• Pendulum: It is used to measure short intervals of time. One complete swing is from one side to the other and back again. It is easier if the stopwatch timing is started when it passes the midpoint. The time for one swing is period. To measure more accurately, measure the time for a large number of swings then calculate average time per swing. As the swings increase, it gets more accurate.