2. Mass
Mass is the quantity of matter in an
object.
Mass is one of the properties of matter
– this means that we can describe matter
by measuring its mass.
We use a triple-beam balance to measure
mass.
Mass is measured in grams, or any metric
conversion of a gram.
3. Weight
Weight is another property of matter – this
means that we can describe matter by
measuring its weight.
Although we use the word weight in
everyday language to refer to how many
pounds and ounces something is, what we
are really referring to is the object’s mass.
In science, weight is not the same thing as
mass.
4. Weight is the product of the object’s
mass and the effects of gravity.
Weight is a Force!
Because weight is a force, it is
measured using a spring scale and
measured in Newtons.
5. The force of gravity is the attractive
force, or pull, between the earth and
all other objects.
Because gravity is a force, and it
affects an object’s weight, weight is a
force as well!
The closer to the surface of the earth
an object is, the stronger the
gravitational attraction on the object.
6.
7. What happens to the
weight of an object as it
moves away from the
Earth?
8. The force of attraction between the
object and the Earth decreases and thus
the object’s weight becomes less.
Keep in mind, the matter that makes up
the object is still present, and unchanged.
All the same atoms and molecules are
there, arranged in the same size and
shape; so the object’s mass does not
change.
9. Measuring mass and weight
The weight of a body depends on the gravitational
field strength that acts on it. On Earth, the
generally accepted value of the gravitational field
strength is 9.8𝑁𝑘𝑔−1. This is equal in value to the
acceleration due to gravity which is equal to 9.8𝑚𝑠
−2. Both are given the symbol 𝑔. The units are
therefore equivalent.
Weight = mass x gravitational field strength
𝑾 = 𝒎 × 𝒈
10. Solve for the following;
A breadfruit has a mass of 2kg. Determine:
a) Its weight on Earth using 𝑔 as 9.8𝑚𝑠−2
b) Its weight on the Moon using 𝑔 as 1.67𝑚𝑠−2
c) How much times greater is the breadfruit’s weight on the
Earth
11. Activity
Calculate your weight here on the Earth using 𝑔 as 9.8 𝑁𝑘𝑔−1.
Remember, mass must be given in kg.
To convert your mass in pounds (lbs.) to mass in kg, divide
the mass in lbs. by 2.2.
