Physical Quantities and Units

Mass kg

Length m

Time s

Current A

Temperature K

Amount of substance mol

Luminous intensity cd candela

The units on either side should be the same

Tera- 10^12

Giga- 10^9

Mega- 10^6

Kilo- 10^3

Centi- 10^-2

Milli- 10^-3

Micro- 10^-6

Nano- 10^-9

Pico- 10^-12

Vector quantity

Describes how far an object is from where it started and in what direction.

Scalar quantity

Describes how far an object has travelled overall, but not the direction it has travelled

Triangle method

Parallelogram method

Coplanar forces can be represented by vector triangle.

In equilibrium, these are closed triangles. The vectors, when joined, form a closed path.

- Check using experimental methods

- Lab instruments and Testing

(d average+/- 1/2 range)unit

When the measured value is always either larger than or smaller than the true value.

Measured values are both larger and smaller than the true value in a random fashion

1. Zero error: instrument has reading when nothing is measured

2. Incorrect calibration of instrument

!NOTICE! Cannot be done by taking repeated readings and average

(only helps with precision of reading)

1. True value= Reading - Zero error

2.Recalibrate instrument

1. Human error: not suitable technique in set-up/instrument

2. Surrounding fluctuations: Temperature, pressure, refraction, friction...

1. Take several readings and average and find the mean value

(*improves BOTH precision and accuracy)

occurs due to the incorrect positioning of the eye when taking a reading on a measuring scale

Wrong reading- pointer's image can be seen in mirror

Correct reading- pointer's image cannot be seen, is right behind the pointer

The Spread

-If the spread is only on one side, Systematic

-If the spread is on both sides, Random

Smallest division that can be measured by the instrument

(Decimal pt: smallest possible reading)

How close the values are to the true value

Taking average increases the precision by one d.p.

work done / time taken

P=E/t