3.2 Forces in action

• Net Force, F = Mass * Acceleration

  Newton is defined as the force required to accelerate a 1 Kg mass by 1 ms^-2
• Examples of Forces =

  Weight = m*g

  Friction

  normal force, (contact force)

  upthrust = in fluids

  Tension = in ropes
• What is the resultant force?

  A) 17N to the right

  
• Drag is proportional to V^2

  acceleration is not constant

  Factors affecting drag =

  Surface area

  Speed
• Acceleration in a fluid:

  A) acceleration = m*g

  B) accelerating at a decreasing rate as drag increases

  C) Terminal velocity

  
• Forces on a slope:

  A) Mg * sin(0)

  B) Mg*cos(0)

  
• Centre of gravity is a point at which the entire weight of an object seems to act

  Centre of mass is a point at which the entire mass of an a object seems to act
• The moment of a force is defined as the product of the force and the perpendicular distance from the pivot to the line of action

  Moment = Force * perpendicular distance

  
• A force couple consists of two equal opposite forces acting in the same plane

  Torque = Force * distance

  
• Triangle of forces is only applicable if object is in equilibrium

  A) No resultant force

  
• Density is defined as mass per unit volume

  Density = mass/volume

  
  

  Pressure is defined as force per unit area

  Pressure = Force/area
• Pressure in a fluid

  Density = mass/Volume

  A) Mass = D*v

  
• Archimedes' Principle

  
  

  States that the upthrust acting on a body submerged in a liquid is equal to the weight of the liquid that has been displaced

  Upthrust = weight of water displaced , m*g

  therefore:

  Upthrust = Density * volume * g

  
• Principle of Moments

  An object will be in equilibrium if:

  There is no net moment

  The sum of clockwise moments is equal to the sum of anticlockwise moments

  What is F2?

  A) 7.5N