Physics: Universal Law of Gravitation
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Questions and Answers

What is the weight of an object on the surface of the moon compared to its weight on Earth?

  • Equal to its weight on Earth
  • One-third of its weight on Earth
  • One-sixth of its weight on Earth (correct)
  • Twice its weight on Earth

    • The weight of an object is the same on the moon and on Earth.

    False

    What is the formula for calculating the weight of an object on the moon?

    Wm = (1/6) × We

    The weight of an object on the moon can be calculated as (1/6) times its weight on the ______.

    <p>Earth</p> Signup and view all the answers

    Match the following terms with their definitions:

    <p>Weight = Force acting vertically downwards due to gravity Mass = Amount of matter in an object Thrust = Force applied to push an object forward Pressure = Force applied per unit area</p> Signup and view all the answers

    Why do cutting tools have sharp edges?

    <p>To exert more pressure on the material</p> Signup and view all the answers

    A truck can run on loose sand without sinking due to its wide tyres.

    <p>True</p> Signup and view all the answers

    What happens to a person standing on loose sand compared to lying down?

    <p>They sink deeper when standing due to greater pressure exerted on the sand.</p> Signup and view all the answers

    What is the formula used to calculate pressure?

    <p>Pressure = Thrust / Area</p> Signup and view all the answers

    The unit of pressure is N/m².

    <p>True</p> Signup and view all the answers

    Calculate the pressure exerted by a wooden block with a mass of 5 kg on an area of 0.02 m².

    <p>2450 N/m²</p> Signup and view all the answers

    The _______ of the thrust on the unit area is referred to as pressure.

    <p>effect</p> Signup and view all the answers

    Match the following terms with their definitions:

    <p>Thrust = Force acting perpendicular to a surface Pressure = Thrust per unit area Area = The measure of a two-dimensional surface Weight = The force due to gravity on an object</p> Signup and view all the answers

    Which of the following statements is true regarding the effect of thrust?

    <p>Thrust is greater when standing than when lying down.</p> Signup and view all the answers

    The area of a side of a rectangle with dimensions 20 cm and 10 cm is 200 cm².

    <p>True</p> Signup and view all the answers

    What is the thrust experienced by a 5 kg wooden block on a surface?

    <p>49 N</p> Signup and view all the answers

    What happens to the force of gravity if the distance between two objects increases by a factor of 6?

    <p>The force becomes 36 times smaller</p> Signup and view all the answers

    The universal law of gravitation explains the motion of planets around the Sun.

    <p>True</p> Signup and view all the answers

    What is the mass of the Earth in kilograms?

    <p>6 × 10^24 kg</p> Signup and view all the answers

    The distance between the Earth and the Moon is approximately _____ km.

    <p>3.84 × 10^5</p> Signup and view all the answers

    Which of the following is NOT explained by the universal law of gravitation?

    <p>The falling of a stone thrown upwards</p> Signup and view all the answers

    The universal law of gravitation has no connection to tides.

    <p>False</p> Signup and view all the answers

    State one example of a phenomenon explained by the universal law of gravitation.

    <p>The motion of the moon around the earth</p> Signup and view all the answers

    Match the following celestial objects with the forces or motions associated with them:

    <p>Earth = Force that binds us to the surface Moon = Motion around the Earth Sun = Gravitational influence on planets Tides = Effect of lunar and solar gravity</p> Signup and view all the answers

    What is the SI unit of pressure?

    <p>Pascal</p> Signup and view all the answers

    A solid does not exert pressure on a surface due to its weight.

    <p>False</p> Signup and view all the answers

    What happens to pressure when the same force acts on a smaller area?

    <p>The pressure increases.</p> Signup and view all the answers

    A block of wood with a mass of 5 kg and dimensions 40 cm × 20 cm × 10 cm exerts pressure of _____ N m–2.

    <p>612.5</p> Signup and view all the answers

    Which side of the block exerts the highest pressure?

    <p>20 cm × 10 cm</p> Signup and view all the answers

    Match the following block dimensions to their corresponding pressures:

    <p>40 cm × 20 cm = 612.5 N m–2 20 cm × 10 cm = 2450 N m–2 40 cm × 10 cm = Unknown</p> Signup and view all the answers

    Liquids and gases are not considered fluids.

    <p>False</p> Signup and view all the answers

    What is the area (in m²) of a rectangular block measuring 40 cm by 20 cm?

    <p>0.08</p> Signup and view all the answers

    What is the upward force exerted by the fluid on an object called?

    <p>Buoyant force</p> Signup and view all the answers

    Buoyant force depends solely on the weight of the object submerged in the fluid.

    <p>False</p> Signup and view all the answers

    What happens to an object that is less dense than the fluid it is immersed in?

    <p>It floats.</p> Signup and view all the answers

    The upward force on an object in a fluid is referred to as __________.

    <p>buoyancy</p> Signup and view all the answers

    Match the following terms with their definitions:

    <p>Buoyant Force = Upward force exerted by a fluid on an immersed object Weight = Force due to gravity acting on an object Pressure = Force exerted per unit area on a surface Density = Mass per unit volume of a substance</p> Signup and view all the answers

    What must be balanced for a bottle to remain immersed in water?

    <p>The weight of the bottle and the upward force of water</p> Signup and view all the answers

    An object made of iron will always sink in water.

    <p>False</p> Signup and view all the answers

    What is the effect of immersing a bottle in water on the perceived weight of the bottle?

    <p>It feels lighter.</p> Signup and view all the answers

    Study Notes

    Universal Law of Gravitation

    • The universal law of gravitation states that the gravitational force (F) is inversely proportional to the square of the distance (d) between two masses.
    • When the distance increases by a factor of 6, the gravitational force decreases by a factor of 36.
    • This law explains several gravitational phenomena:
      • The force keeping objects on Earth.
      • The moon's orbit around Earth.
      • The planets' orbits around the Sun.
      • Tidal forces caused by the moon and Sun.

    Calculating Gravitational Force

    • Mass of Earth: 6 × 10²⁴ kg
    • Mass of Moon: 7.4 × 10²² kg
    • Distance between Earth and Moon: 3.84 × 10⁵ km
    • Gravitational constant (G): 6.7 × 10⁻¹¹ N m²/kg²

    Free Fall

    • Free fall is observed when an object, such as a stone thrown upwards, reaches a peak and falls back due to gravitational force.
    • An object's weight on the Moon is 1/6 of its weight on Earth.
    • For example, an object weighing on Earth will weigh 1.67 N on the Moon.

    Weight vs. Mass

    • Mass is the quantity of matter in an object; weight is the gravitational force acting on that mass.
    • Weight on the Moon is reduced to 1/6 of that on Earth due to lower gravitational strength.

    Thrust and Pressure

    • Thrust is the force acting perpendicular to a surface; it depends on the area over which it acts.
    • Pressure is defined as thrust per unit area (Pressure = Thrust/Area).
    • The thicker the pressure area, the lower the pressure exerted by an object, e.g., standing vs. lying on sand.

    Pressure Calculation

    • Example: A wooden block with a mass of 5 kg exerts different pressures based on its orientation.
    • Pressure exerted on a 20 cm × 10 cm side results in 2450 N/m², while on a 40 cm × 20 cm side it's 612.5 N/m².

    Fluid Pressure

    • All fluids exert pressure due to their weight and transmit this pressure undiminished in all directions.
    • In a contained fluid, pressure operates on the surfaces of its container.

    Buoyancy

    • Buoyant force, or upthrust, is the upward force experienced by an object immersed in a fluid.
    • Objects will float or sink in water depending on their density relative to the fluid.
    • Boats crafted from iron or steel float in water due to the principle of buoyancy, which considers fluid density.

    Understanding Floating and Sinking

    • The weight of a submerged object is counteracted by the buoyant force exerted by the fluid.
    • The condition for floating is met when the weight of the fluid displaced equals the weight of the object.

    Key Concepts Summary

    • Inverse-square law describes gravitational interactions.
    • Differentiating weight and mass is fundamental in gravitational studies.
    • Pressure principles explain various phenomena including buoyancy and behaviors of objects on different surfaces.

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    Chapter 9 Gravitation PDF

    Description

    Explore the concepts of the universal law of gravitation, including the relationship between mass and distance. Understand how this law impacts various gravitational phenomena, such as orbits and free fall. Test your knowledge on calculating gravitational force and the differences in weight on the Moon and Earth.

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