1. Weight, Grade 10 Physics, Gravity and Mechanical Energy
    Weight is the gravitational force that the Earth exerts on any object. The weight of an objects
    gives you an indication of how strongly the Earth attracts that body towards its centre. Weight
    is calculated as follows:
    Weight = mg​
    • where m = mass of the object (in kg)
    • and g = the acceleration due to gravity (9,8 m·s$^{−2}$)
    For example, what is Sarah’s weight if her mass is 50 kg. Sarah’s weight is calculated according to:
    Weight = mg = (50 kg)(9,8 m · s$^{−2}$) = 490 kg · m · s$^{−2}$ = 490 N
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    Important: Weight is sometimes abbreviated as F$_{g}$ which refers to the force of gravity. Do not use the abbreviation ’W’ for weight as it refers to ’Work’.
    Now, we have said that the value of g is approximately 9,8 m·s$^{−2}$ on the surface of the Earth.
    Worked Example 1: Determining mass and weight on other planets
    Question:
    Sarah’s mass on Earth is 50 kg. What is her mass and weight on Mars?
    Answer
    Step 1 : Determine what information is given and what is asked

    m (on Earth) = 50 kg
    m (on Mars) = ?
    Weight (on Mars) = ?
    The actual value varies slightly over the surface of the Earth. Each planet in our Solar System has its own value for g. These values are listed as multiples of g on Earth in Table 4.1
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    Table 4.1: A list of the gravitational accelerations at the surfaces of each of the planets in our solar system. Values are listed as multiples of g on Earth. Note: The ”surface” is taken to mean the cloud tops of the gas giants (Jupiter, Saturn, Uranus and Neptune).
    Step 2 : Calculate her mass on Mars
    Sarah’s mass does not change because she is still made up of the same amount of matter. Her mass on Mars is therefore 50 kg.
    Step 3 : Calculate her weight on Mars
    Sarah′s weight = 50 × 0,38 × 9,8 = 186,2 N
    2/ Differences between Mass and Weight
    Mass is measured in kilograms (kg) and is the amount of matter in an object. An object’s mass does not change unless matter is added or removed from the object. The differences between mass and weight can be summarised in the following table:
    [​IMG]
    Exercise: Weight
    E - 1.
    A bag of sugar has a mass of 1 kg. How much does it weigh:
    (a) on Earth?
    (b) on Jupiter?
    (c) on Pluto?
    E - 2. Neil Armstrong was the first man to walk on the surface of the Moon. The gravitational acceleration on the Moon is 16 of the gravitational acceleration on Earth, and there is no gravitational acceleration in outer space. If Neil’s mass was 90 kg, what was his weight:
    (a) on Earth?
    (b) on the Moon?
    (c) in outer space?
    E - 3. A monkey has a mass of 15 kg on Earth. The monkey travels to Mars. What is his mass and weight on Mars?
    E - 4. Determine your mass by using a bathroom scale and calculate your weight for each planet in the Solar System, using the values given in Table 4.1

    High School Students Studying the Sciences Physics
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