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2.9.1 Gravitational Field

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A gravitational field as a region in which an object experiences a force due to gravitational attraction.

Gravitational Field Strength

  1. The gravitational field strength at a point in the gravitational field is the gravitational force acting on a mass of 1 kg placed at that point.
  2. The unit of gravitational field strength is N/kg.
  3. The gravitational field strength is denoted by the symbol "g".
    4. g = Gravitational Field Strength
    F = Force acted on an object
    m = mass of the object.

Gravitational Acceleration

  1. The gravitational acceleration is the acceleration of an object due to the pull of the gravitational force. It has the unit of ms-2
  2. The symbol of gravitational acceleration is " g ".
  3. Gravitational acceleration does not depend on the mass of the moving object.
  4. The magnitude of gravitational acceleration is taken to be 10ms-2.

Important notes:

  1. Gravitational acceleration does not depend on the mass of the moving object.
  2. The magnitude of gravitational acceleration is taken to be 10ms-2.

Gravitational Field Strength vs. Gravitational Acceleration

  1. Both the gravitational field strength and gravitational acceleration have the symbol, g and the same value (10ms-2) on the surface of the earth.
  2. When considering a body falling freely, the g is the gravitational acceleration.
  3. When considering objects at rest, g is the Earth’s gravitational field strength acting on it.

Free Falling

  1. Free falling is a motion under force of gravity as the only force acting on the moving object.
  2. Practically, free falling can only take place in vacuum.

Case of Free Falling 1 - Falling from High Place

When an object is released from a high place,

  1. its initial velocity, u = 0.
  2. its acceleration is equal to the gravitational acceleration, g, which taken to be 10ms-2 in SPM.
  3. the displacement is the of the object when it reaches the ground is equal to the initial height of the object, h.

Case of Free Falling 2 - Launching Object Upward

If an object is launched up vertically,

  1. the acceleration = -g (-10ms-2)
  2. the velocity become zero when the object reaches the highest point.
  3. the displacement of the object at highest point is equal to the vertical height of object, h
  4. the time taken for the object to move to the maximum height = the time taken for the object to fall from the maximum point to its initial position.