Topic 15: Forces and Matter

• What happens when a single force is applied to an object?


  The object moves in the force's direction
• What occurs when forces are applied inwards from opposite sides?


  The object compresses
• What is a reaction force in the context of a spring?


  A force from the fixed point of the spring
• What does deformation mean?


  Changing shape
• What is elastic deformation?


  The object returns to its original shape
• Give an example of elastic deformation.


  An elastic band
• What is plastic deformation?


  The object does not return to its original shape
• Give an example of plastic deformation.


  A spring pulled too far
• What does Hooke's Law state about the extension of a spring?


  It is directly proportional to the force applied
• What does the linear section on a Force/Extension graph indicate?


  It follows Hooke's Law
• What is the gradient of the linear section on a Force/Extension graph?


  Spring constant
• What is the elastic limit on a Force/Extension graph?


  The point it stops being linear
• What characterizes the non-linear section of a Force/Extension graph?


  It does not follow Hooke's Law
• What happens if the graph is just linear with no non-linear section?


  The material is brittle and snaps
• How is work done calculated from a Force/Extension graph?


  Area under the graph
• What is atmospheric pressure?


  Total weight of air above a unit area
• How does atmospheric pressure change with altitude?


  It decreases with increasing height
• Why does atmospheric pressure decrease with height?


  Fewer air molecules above the unit area
• What is the relationship between pressure in a fluid and depth?


  Pressure increases with greater depth
• What is the effect of density on pressure in a fluid?


  Greater density leads to greater pressure
• What is the formula for pressure in a fluid?


  Pressure = force / area
• What determines if an object floats?


  Weight less than displaced water weight
• How does a boat float in water?


  It displaces its weight in water
• What is buoyancy?


  Upwards force counteracting the object's weight
• How is buoyancy force calculated?


  Equal to weight of fluid displaced
• Why does a ping pong ball float on water?


  Its density is less than water's density
• What happens to pressure as depth increases in a fluid?


  Pressure increases with greater depth
• What is the formula for pressure due to a column of liquid?


  Pressure = height × density × acceleration due to gravity