Unit 5a- forces

• Force


  A push or pull that acts on an object due to its interaction with another object. Forces measured in Newtons
• Balanced forces = when the forces acting on an object have equal magnitude and act in opposite directions, the object will be balanced
• Stationary-Balanced, balanced forces are equal in magnitude and act in opposite direction. If the arrow length is equal (so same magnitud) the box will remain stationar.
• Arrow length- moving


  Thrust pushes forwards, drag pulls backwards. Same magnitude
• Balanced Forces


  • Equal in magnitude, act in opposite directions
• Balanced force-moving: Travel at a constant speed, no change. Thrust and drag cancel out.
• Stationary - Unbalanced, Starts to move
• Moving-Unbalanced, Thrust and drag do not cancel out, accelerate or decelerate. Will now be a change.
• Resultant force: A single force that has the same effect as all the original forces acting together
• Calculating Resultant Force


  1. Forces in same direction: Add them together

  2. Forces in opposite direction: Big Force - Small force. Always goes in direction of original big force.
• Work Done


  Force x Distance W=F x s
• Elasticity: When a force is put onto an object it can change its shape, speed, direction of movement
• Elastic Deformation


  • Object returns to original shape after force is removed
• Inelastic Deformation


  • Object stays deformed after force is removed
• Elastic Objects


  • Metal spring
• Inelastic Objects


  • Plasticine
• Elasticity Equation


  Force = Spring Constant x Extension F= k x e
• Spring Constant: Measurement of how stiff a material is (larger spring constant = stiffer)
• Extension: Difference in length (new - old)
• Not all extensions can be measured in metres, may need to convert units. Millimetres to metres = divide by 1000, centimetres to metres = divide by 100.
• Moments: Acts around a point of rotation called a pivot or fulcrum
• Moments Equation


  Moment = Force x Perpendicular Distance M = F x d
• Moments can be clockwise or anticlockwise around a pivot
• Levers: consists of a pivot, effort and load. Make use of moments to act as a force multiplier, so easier to move heavier objects.