1. Gravitational Force
the gravitational field strength is the amount of force per unit mass acting on an object in the field
the gravitational field strength is 9.81 N/kg [down] which is the same as the acceleration due to gravity thus the symbol 𝑔 is used for both
to determine the force of gravity acting on an object at the Earth’s surface we use the formula:
𝐹 𝑔 = m 𝑔
3.1 Prac. #2-5

2. Variations in Field Strength
the further you are from the center of the Earth, the smaller the gravitational field strength
since the Earth is not a perfect sphere, the g.f.s. will vary according to your location N
9.83 N/kg
9.78 N/kg
equator S
9.83 N/kg
the equator is actually further from the center of the Earth than the poles (about 21 km)
the g.f.s. is less at the equator than poles (refer to table 2 pg. 87)
3.1 Prac. #9,10
Equator Video
Real Equator Video

3. Mass vs. Weight
mass is the quantity of matter in an object
it does not change according to position on Earth
measured in kilograms (kg)
weight is the force of gravity on an object ( 𝐹 𝑔 )
to calculate weight use: 𝐹 𝑔 = m 𝑔
measured in Newtons (N)
\your weight may vary according to your position on Earth but your mass remains the same
Mass vs. Weight Video
Mr. Edmonds Mass vs. Weight
3.1 Prac. #6-8
UC #2-9