physics notes ( chapter 1 )

physical quantities

it can be measured and consists of magnitude and a unit

base quantity

• length

• mass

• time

• electric current

• thermodynamic temperature

• amount of substance

SI unit

1. length = metre

2. mass = kilogram

3. time = second

4. electric current = ampere

5. thermodynamic temperature = kelvin

6. amount of substance = mole

instrument

measuring tape = zero to several metres like 0.1cm or 1mm example = a person waist

metre rule = zero to one metre like 0.1cm to 1mm example = height of a table

digital calipers = zero to 15 cm like 0.001cm to 0.01mm example = diameter of a test tube

digital micrometer screw gauge = zero to 2.5 cm like 0.0001cm or 0.001mm example = diameter of a wire

parallax error

when the eyes is not positioned in perpendicular ( directly above ) to the ruler

pendulum

a bob that will swing back and forth at regular intervals

oscillation

each complete to and fro motion

period

time taken for one complete oscillation by the pendulum

scalar quantities

physical quantities that only have magnitude

vector quantities

physical quantities that have magnitude and direction

example of scalar quantities

distance

speed

mass

energy

time

example of vector quantities

displacement

velocity

acceleration

force

weight

distance

total length covered regardless of the direction of motion

displacement

total distance covered in a straight line in a specified direction

speed

the distance moved per unit time

speed formula

= distance divide by time

SI unit for speed

= metre per second

velocity

is the rate of change of displacement

velocity formula

displacement divided by time