Physical Quantity O level

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Summary

O level Physical Quantity

- A physical quantity is a quantity that can be measured using an instrument.

- It consists of a magnitude(number) and a unit

- SI unit: International Standard of Unit

Base Quantities VS Derived Quantity

- Base: Length(m), Mass(kg), Time(s), Temperature(K), Electricity(A), Amount of Substances(mol)

-Derived- two more base quantities eg. speed(Distance/Time), Area(Length x Breadth) etc

Prefixes( required to know symbol, value)

- Tera

- Giga

- Mega

- Kilo

- Deci

- Centi

-Milli

- Micro

- Nano

Scalar quantity

- Quantity that only has magnitude but no direction

-Examples include: Distance, Time, Mass

Vector Quantity

-Quantity that has magnitude and direction

- Examples include, Displacement, Force, Acceleration

Addition of vectors- Tip to Tail or parallelogram method

Parallax Error- It is a human error that occurs due to the incorrect position of the human eye when taking a reading or when the object is not touching the markings of the scale

- Can be avoided

Instrumental Error- Error caused by Instruments such as vernier calipers or micrometer screw gauge due to instrumental fault.

- Zero Error can be deducted from the final measurement reading

Period of a simple pendulum- Time taken for one complete oscillation

Unit: seconds

Step 1: Swing the bob into oscillation, let the oscillation stabilise first

Step 2: Find the time taken 

for 20 oscillations

Step 3: Repeat for at least 3 times

Step 4: Find the average of the timings taken

Step 5: Divide the average by 20 to find out the time taken for 1 oscillation

Why is there a need to find the average/find 20 oscillation- To reduce Human Reaction Error that may occur during the taking of the readings using a stopwatch

Period of the pendulum is only affected by 

1. Length of the string

2. Gravitational field Strength

The End

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