SCIENCE

• Force


  Can be operationally defined based on observed effects, describing what it does
• Forces do not always cause motion
• Forces acting on objects

  • A girl sitting on a chair
  • A boy pushing a wall
  • A woman throwing a ball
• Forces can produce changes in motion
• Magnitude


  Size or strength of the force, commonly expressed in Newtons (N)
• Direction


  Where the object goes, indicated by the arrowhead
• Point of application


  Location where the force is applied
• Line of action


  Straight line passing through the point of application and parallel to the direction of force
• Types of forces


  • Contact forces
  • Non-contact forces
• Contact forces


  Forces where objects touch or contact with each other
• Contact forces


  • Applied force
  • Friction force
  • Normal force
• Applied force


  Force given to a person or object by another person or object
• Friction force


  Force acting against or opposite an object in contact with, making the movement slow down
• Normal force


  Force that acts perpendicular to the surface of the object in contact
• Non-contact forces


  Forces exerted without physical contact, like gravitational and magnetic forces
• Gravitational force


  Force that pulls objects towards the ground
• Magnetic force


  Force of attraction or repulsion between magnetic fields
• Balanced forces


  Equal in magnitude but opposite in direction, do not cause a change in motion
• Gravity


  The force of attraction exerted by the mass of the celestial body where the object is attracted to
• Magnetic forces


  Forces exerted on a field of attraction or repulsion as in the case of magnets and other magnetic materials
• Magnets and magnetic materials have two poles - the north and south poles
• Attraction


  Occurs when two poles are not the same, a positive and a negative
• Repulsion


  Takes place with the same poles, positive-positive and negative-negative
• Balanced forces


  Forces that are equal in magnitude but opposite in direction
• Balanced forces do not cause a change in motion
• Unbalanced forces


  Forces that cause a change in the motion of an object
• Unbalanced forces are not equal and in opposite direction
• Net force/Resultant force


  The sum of all forces acting on an object
• When an object is at rest, a zero net force would make the object remains at rest
• When the object is moving, a zero net force would make the object maintain its velocity at a given time interval
• When the net force is not zero, the object's velocity will change
• A net force exerted to an object at rest may cause the object to move
• In a moving object, a net force will increase its velocity when the force is in the same direction of its motion
• If the net force is in the opposite direction of the object's motion, the force will reduce the object's velocity
• When the net force acts sideways on a moving object, the direction of the object's velocity changes
• Forces can be applied to objects in different directions at the same time
• It is important to identify all the forces acting on the object which cause change in the motion