resultant forces and work done

• Forces


  Responsible for all the interactions between particles and objects
• Categories of forces


  • Contact forces
  • Non-contact forces
• Forces


  Can be added up as vectors
• If the weight of the box (acting downwards) is 50 N and the normal reaction force (acting upwards) is 50 N, the forces are balanced and the resultant force is zero
• If the weight of the box (acting downwards) is 50 N and the air resistance (acting upwards) is 20 N, the forces are unbalanced and the resultant force is 30 N downwards
• Gravity


  One of the most important forces in the universe
• Gravitational field


  An object with mass in a gravitational field experiences a force known as weight
• How to calculate work done

  Work done = force × distance moved in the direction of the force
• Work is done when energy is transferred from one store to another
• Work is also done when a force causes an object to move
• When work is done against frictional forces acting on an object, the object's temperature increases
• Work done


  The amount of energy it takes to do a task, measured in joules (J)
• One joule of work is done when a force of 1 N causes a movement of 1 m