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Chapter summary (ESCJT)

Presentation: 27JC

  • Newton's Second Law: The resultant force acting on a body will cause the body to accelerate in the direction of the resultant force The acceleration of the body is directly proportional to the magnitude of the resultant force and inversely proportional to the mass of the object.

  • Newton's Third Law: If body A exerts a force on body B then body B will exert an equal but opposite force on body A.

  • Momentum: The momentum of an object is defined as its mass multiplied by its velocity.

  • Momentum of a System: The total momentum of a system is the sum of the momenta of each of the objects in the system.

  • Principle of Conservation of Linear Momentum: `The total linear momentum of an isolated system is constant' or `In an isolated system the total momentum before a collision (or explosion) is equal to the total momentum after the collision (or explosion)'.

  • Elastic collision: both total momentum and total kinetic energy are conserved.

  • Inelastic collision: only total momentum is conserved, total kinetic energy is not conserved.

  • Impulse:the product of the net force and the time interval for which the force acts.

  • Law of Momentum: The applied resultant force acting on an object is equal to the rate of change of the object's momentum and this force is in the direction of the change in momentum.

  • Impulse-momentum theorem: the impulse is equal to the change in momentum.

Physical Quantities



Unit name

Unit symbol

Mass (\(m\))




Velocity (\(\vec{v}\))


metre per second


Momentum (\(\vec{p}\))


kilogram metres per second


Kinetic energy (\(KE\))






newton seconds


Table 2.1: Units used in momentum and impulse.