Forces AS

• “The upthrust force on a

  body submerged in a liquid

  is equal to the weight of

  the liquid that is displaced.”
• Density = Mass / volume.
• Upthrust = Weight of water displaced.
• Weight of water displaced = Volume of water displaced x Density of water.
• Pressure = Force / area.
• Weight = mass x gravitational field strength.
• Weight = mass x g (9.81 m/s2).
• Acceleration due to gravity is the same everywhere on Earth, but it varies from place to place depending on latitude.
• One Newton is the force required to accelerate a mass of 1 kg by 1 m/s-2
• moments must be balanced or the object will turn
• a moment is the turning effect of a force
• a couple is a pair of forces
• moment = force x perpedicular distance (F x d)
• Moments are also known as torques
• A pivot point is where a rotating object turns around
• If there is no resultant moment, then the object won't move
• The line of action of a force passes through its pivots
• If two moments have equal magnitudes but opposite directions, they cancel out
• When an object is in equilibrium it has no resultant force acting on it
• The centre of gravity is the balance point of an object
• The resultant moment is equal to the sum of all moments acting on an object
• To balance a lever, we need to find the centre of gravity or centre of mass
• pressure = depth x density of liquid x gravitational field strength