Transcript Document

Mass
What is mass?
Mass is the measure of the amount of substance in a body
Units
SI units: kg
Other units: g, tonne
Conversion
1 kg = 1000g
1 ton = 1000kg
Can calculate what is 1 ton in grams?
If mass in kilograms,
what about weight?
Shouldn’t weight be
in kilograms instead?
Mass
Measuring Mass
The instruments used to measure mass are
1. Electronic balance
2. Beam balance
Weight
What is weight
The weight of a body is the pull of gravity on that body
Units
SI units: N (newton)
Newton’s 2nd law
Since weight is a
force, it must be a
vector… So which
direction is our
weight pointing?
Force = mass x acceleration
Weight = mass x acceleration due to gravity
W
= m x
g
Weight
Acceleration due to gravity
Planets
Sun
Mercury
Venus
Earth
Earth
Moon
Mars
Jupiter
Saturn
Uranus
Neptune
Pluto
Acceleration Due to Gravity Comparison
Acceleration Due
Mass [kg] Radius [m]
g / g-Earth
to Gravity, "g" [m/s2 ]
1.99 x 1030
3.18 x 1023
4.88 x 1024
5.98 x 1024
7.36 x 1022
6.42 x 1023
1.90 x 1027
5.68 x 1026
8.68 x 1025
1.03 x 1026
1.40 x 1022
6.96 x 108
2.43 x 106
6.06 x 106
6.38 x 106
1.74 x 106
3.37 x 106
6.99 x 107
5.85 x 107
2.33 x 107
2.21 x 107
1.50 x 106
274.13
3.59
8.87
9.81
9.81
1.62
3.77
25.95
11.08
10.67
14.07
0.42
27.95
0.37
0.90
1.00
0.17
0.38
2.65
1.13
1.09
1.43
0.04
Weight
Measuring Mass
The instruments used to measure mass are
1. Electronic balance
2. Beam balance
Mass Vs Weight
Get into groups of 4 and discuss:
The differences between mass and
weight
10mins
Class Activity
•Give the raw egg hard spin on its side
•Stop the spin by placing a fingertip on the
egg, the quickly lift the finger
•What do you observe as you lift the
finger?
Inertia
What is inertia?
It is the reluctance of a body to start moving if it
is stationary in the first instance
OR
It is the reluctance of a body to stop moving if it is
moving in the first instance
Inertia
100kg Vs 20kg
Who is easier to push?
Who is easier to stop?
100kg
20kg
Density
Container A
Container B
Can you tell the difference between the 2 containers?
Density
What is density?
Density is defined as mass per unit volume
Density = mass/volume
Units
M
SI units: kg/m3
Other units: g/cm3
D
V
My Dear Valentine
Density
Object
Mass/g Vol/cm3
Aluminium
sheet
50
18.52
Gold bracelet
150
Water
Density
g/cm3
Sink or
Float?
2.70
Sink
7.89
19.0
Sink
500
500
1
---
Ice
10
10.87
0.92
Float
Block of
pinewood
800
1600
0.5
Float
Density
Get into groups of 4 and discuss:
How you would help the King identify
whether the crown was made of
pure gold or not?
Write your answers on the mahjong paper provided
Present your solution to the class next lesson
Concept Map
kg/m3
Densit
y
Mass per unit
volume
defined as
related
to mass
by
D = M/V
related to
density by
Mass, m
defined
as
kg
related to
weight by
is a
measure of
W=mxg
related
to mass
by
N
Weight
where
defined
as
Amount of
substance in a
body
inertia
g is the gravitational force
per unit mass acting on an
object
Gravitational force
acting on an object