Science 8 (physics)

• Balanced and Unbalanced Forces Terms

  • Magnitude
  • Direction
  • Point of Application
  • Line of Action
• Newton's Three Laws of Motion

  • 1. Law of Inertia - A body will remain at rest or move at constant velocity unless acted upon by an external net or unbalanced force.
  • 2. Law of Acceleration-The acceleration of an object is directly proportional to the magnitude of the net force acting on it and is inversely proportional to its mass.
  • 3. Law of Interaction-For every action, there is an equal and opposite reaction.
• 1 Newton (N) = 1 kg/ms²
• The books fall to the ground at the same rate (acceleration) even if they differ in mass. Since they were released from the same height of the same time, they will reach the ground at the same time. This acceleration, known as acceleration due to gravity, is the same for all objects on earth and is
• In the case of circular motion, the whirling object accelerates not due to the change in its speed but to the change in the direction of its velocity


  The object accelerates inwards (centripetal) thereby covering a circular path
• Differences between Balanced and Unbalanced Forces

  • Action acts on one object, while the reaction acts on another object.
  • Two forces are opposite to each other in terms of direction.
  • Two forces act upon the same object.
• Conditions for Work to be Done

  • If the force you exert does not make the object move.
  • If the object you push moves a distance in the direction towards which you are pushing it.
  • If the force you exerted does not make the object move in the same direction as the force you exerted.
• Work


  F = force applied

  W = Fd

  d = displacement of the object
• Unit of work


  unit of force x unit of displacement = Nm or joules (J)
• Kinetic Energy


  • Energy of a moving object (energy of motion)

  W = work done

  KE = 1/2 * m * v ^ 2
• Potential Energy


  • Energy gained or lost by an object/stored energy

  PE = mgh
• Power


  The rate of doing work or the rate of using energy

  \mathfrak{P} = Work / time = Energy / time

  1 watt = 1 joule / second
• Work is a way of transferring energy
• When work is done by an object

  It loses energy
• When work is done on an object

  It gains energy
• The energy of an object enables it to do work
• Heat


  A form of energy

  Transfers from an object of higher temperature to an object of lower temperature

  Can be transferred through conduction, convection, or radiation "energy in transit"
• Temperature


  A measure of the average kinetic energy of the particles

  Does not depend on the mass of the object
• Thermal Energy


  Energy that is contained in an object due to the motion of its particles
• Thermal Expansion


  • Effect of heat transfer: tendency of matter to change its shape, area, and volume in response to a change in temperature
• Phase Change


  • May occur when heat is added to or taken out from an object
• Amount of heat transferred depends not only on the temperature of the material, it also depends on the mass of amount of material
• Objects with greater mass have more thermal energy and can transfer more heat
• Heat Capacity


  Amount of heat required to increase the temperature of one unit mass of a given material by one Celsius degree: specific heat capacity (c) calorie

  \mathfrak{c} = specific heat capacity

  H = mc*Delta*T

  m = mass

  Delta*T = Final Temp. - Initial Temp.