New Series: 25 videos covering the IGCSE Physics syllabus from A to Z.
Current Video: Chapter 1 - Making Measurements.
Importance of Accurate Measurement
NASA Mars Orbiter Incident: Used incorrect units (pounds force seconds instead of Newton seconds) causing mission failure and a loss of millions of dollars.
Measuring Length
Tools: Ruler, precautions for accuracy.
Wire example: Must be straight, start at zero point, and ruler must be calibrated.
Paper thickness: Measure stacked papers and divide by the number of sheets.
Thread: Lay thread on a line and measure with a ruler.
SI Unit: Meter (m), can use prefixes like centi-, deci-, milli-, micro-, kilo-.
Example Problem
Determine Circumference: Use a marker and roll the object to measure with a ruler. Calculate the circumference by subtracting starting point from the end point after one cycle.
Measuring Volume
**Formulas for Regular Shapes: **
Cubic: Volume = length x width x height
Sphere: Volume = 4/3 πr³
Cone: Volume = 1/3 πr²h
Irregular Shapes: Water displacement method using measuring cylinder.
SI Unit: Cubic meter (m³), can use prefixes.
Measuring Time
**Tools: ** Clocks (analog and digital), simple pendulum.
Digital clocks provide higher accuracy with milliseconds and nanoseconds.
Pendulum: Used when other clocks are not available, oscillates at a constant rate.
Period: Time for one complete oscillation.
Example Problem
Running Speed: Calculate time elapsed for one lap and use it to predict time for 5 km by converting and scaling the time.
Measuring Density
Definition: Density = Mass / Volume
Dense object: More matter in small volume.
Less dense object: Less matter in same volume.
**SI Units for Density: **
Gram per cubic centimeter (g/cm³)
Kilogram per cubic meter (kg/m³)
Example Problems
Density Calculation: Find the density using given mass and volume.
Mass per Match: Determine mass of one match by subtracting box's mass from total mass and dividing by number of matches.
Volume of Match: Convert dimensions to cm and multiply to find volume.
Total Density: Use mass and volume to calculate the density of a match.
Liquid Density: Use measuring cylinder and balance to find mass and volume of liquid, then calculate density.