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• Force

  A push or a pull
• Types of contact forces

  • Friction
  • Elastic force
  • Tension force
  • Normal force
• Friction

  • The force that opposes motion
  • Exists between surfaces of 2 objects in contact
  • Useful: slows down bicycle, air rubs against parachute, grip needed, stops hands slipping
  • Nuisance: wears away materials, slows down moving objects, reduces efficiency of machines, produces heat
  • Ways to reduce: smooth surfaces, ball bearings, lubricants, streamlined shapes, layer of air
• Elastic force

  Forces acting on a stretched/compressed elastic object to return to its original shape
• Tension force

  A pulling force applied by an object when it's stretched
• Normal force

  The force that a surface exerts on an object
• Non-contact forces

  Forces that act without physical contact between objects
• Gravitational force

  The force that attracts objects towards each other
• Magnetic force

  The push or pull between magnets only, or magnets on magnetic materials
• Weight

  The gravitational force acting on an object
• Differences between mass and weight

  • Mass: the amount of matter in an object, constant regardless of location
  • Weight: the gravitational force acting on an object, may vary according to location's gravity
• Applying a force can cause an object to change its state of rest or motion
• How a force can affect a moving object

  • Decrease its speed
  • Increase its speed
  • Change its direction
• Resultant force

  The overall force after considering all forces acting on a body
• There is resultant force when forces are unbalanced
• Resultant force = 0N means the object can either be at rest or moving at a constant speed in the same direction
• A force applied on an object can cause a turning effect about a fixed point called a pivot
• When the force is applied at a distance further away from the pivot, it is easier to turn something as the turning effect is greater
• The greater the distance away from the pivot, the lesser the applied force required
• Pressure

  The force acting perpendicularly per unit area
• Factors affecting pressure

  • Force
  • Area
• Atmospheric pressure

  The pressure exerted by the air in the Earth's atmosphere
• Work done results in a transfer of energy
• When energy is transferred, work is done through the application of a force
• Conditions for work to be done

  • There is a force acting on the object
  • The object moves
  • The movement of the object is in the direction of the force
• Energy

  The ability to do work
• SI unit of energy

  J or kJ
• Living and non-living things require energy to keep them alive and function respectively
• Types of energy

  • Thermal energy
  • Light energy
  • Sound energy
  • Electrical energy
  • Nuclear energy
  • Potential energy
  • Kinetic energy
• Thermal energy

  The energy that flows from a region of higher temperature to a region of lower temperature
• Light energy


  The energy that enables us to see, given out by luminous objects
• Sound energy

  The energy produced when objects vibrate
• Electrical energy

  The energy that results from the flow of charged particles
• Nuclear energy

  The energy stored in the nucleus of an atom, released during nuclear fission or fusion
• Types of potential energy

  • Chemical potential energy
  • Gravitational potential energy
  • Elastic potential energy
• Chemical potential energy

  Energy stored in food, fuels, and electric cells that can be released through chemical reactions
• Gravitational potential energy

  The energy an object has due to its elevated position
• Elastic potential energy

  The energy an object has when it's pushed or pulled
• Kinetic energy

  The energy a body possesses due to its motion
• When an object is in a higher position with respect to the ground, it has more gravitational potential energy than in a lower position