Science Y8 EndOfYears

• what does contact mean?

  a force that arises when objects are touching
• what does non-contact mean?

  A force that arises even though objects are not touching
• If an object is not moving, the forces on it must be balanced.

  This means the object is in equilibrium.
• We use arrows to represent the forces.

  The direction of the arrow represents the direction of the force.

  The length of the arrow represents the size of the force.
• When two objects are touching they exert a contact force on each other. We call this the normal reaction force.
• what is the resultant force?

  A single force that which has the same effect on an object as the set of forces it replaces it.
• what is the unit of force?

  Newtons
• Friction:


  When two solids slide past each other they experience a resistive force called friction
• resistive force:


  A resistive force is a force that acts against an object's direction
• A fluid is a substance that can flow. Fluids are either liquid or gas.

  Anything that moves through a fluid will experience a resistive force called drag.
• drag:


  The resistive force a gas or a liquid.
• Drag increases when:

  • Moves faster through the fluid
• Drag increases when:

  • Moves faster through the fluid
  • Has a larger surface changing the direction of movement
• What is Streamlining?


  Streamlining creates a shape that allows fluid to flow easily around an object.
• what is deformation?


  if a material changes shape
• What are elastic materials?


  if a material changes shape, and then changes back to its original shape
• what is permanent deformation?


  if a material changes shape and does not change back.
• what is permanent deformation?


  if a material changes shape and does not change back.
• Materials can be squashed or stretched by forces.
• what is compression?
• compression:


  force squashing or pushing together
• tension:


  force stretching a material
• linear relationships:


  When changing the independent variable causes the same change in the dependent variable.
• Pressure:


  Pressure is defined as force per unit area.

  For the same force, a larger area has the lower pressure and a smaller area has a higher pressure .
• Unit of pressure:


  Pascal
• pressure = force/area
• area = force/pressure
• force = pressure X area
• molecule:


  two or more atoms joined together chemically
• pressure in a fluid acts in all direction
• Pressure in a fluid increases with depth
• atmospheric pressure


  The pressure exerted by the weight of the air above that point
• what causes atmospheric pressure?


  pressure executed by the weight of the air molecules
• what happens to atmospheric pressure with altitude?


  Pressure will decreased as altitude increases as there are less molecules
• Particle in a fluid have a weight which means they push down on anything below them.
• Increasing in depth in a fluid that more particles are above an object, the pressure increases.
• Define density:


  mass per unit volume

  If an object is less dense than water it will float, if its more dense it will sink
• define upthrust:


  Upward(buoyancy) force acting on an object in a fluid
• The buoyancy force provided by water is called upthrust.

  An object will displace water when its submerged.The weight of the displaced water is equal to the upthrust
• If a object floats:

  The weight of the displaced water is equal to the weight of the object. This means the upthrust is equal to the weight and the resultant force is zero.

  If a object sinks:

  The weight of the displaced water is not equal to the weight of the object.

  This means the upthrust is less than the weight and the resultant force is still pulling downwards.