Topic 15 Forces and Matter

• What are the three types of deformation mentioned in the study material?

  Elastic deformation, plastic deformation, and linear elastic distortion

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

  The object will just move in the force’s direction
• What occurs when a spring is fixed at one end and a force is applied at the other end?

  More than one force is applied to the spring, including a reaction force from the fixed point
• What does deformation mean in the context of springs?

  Changing shape

  
• What is elastic deformation?


  The object returns to its original shape when the load has been removed

  
• Give an example of elastic deformation.

  An elastic band

  
• What is plastic deformation?


  The object does not return to its original shape when the load has been removed

  
• Provide an example of plastic deformation.


  A spring when pulled too far

  
• What is the formula for Hooke's Law?

  F = kx
• What does the spring constant \( k \) represent?

  The force required to extend a spring per metre
• In Hooke's Law, what does \( F \) represent?

  The force applied to the spring, measured in Newtons (N)
• In Hooke's Law, what does \( x \) represent?

  The extension of the spring, measured in meters (m)
• What does it mean if a spring follows Hooke's Law?

  The extension of the spring is directly proportional to the force applied
• What does the gradient of the linear section on a Force/Extension graph represent?


  The spring constant \( k \)

  
• What is the elastic limit of a spring?

  The point at which it stops being linear and does not obey Hooke’s Law
• What characterizes a non-linear line section on a Force/Extension graph?

  It does not follow Hooke’s Law and indicates plastic deformation

  
• What happens if the graph is just linear with no non-linear end section?

  The material is considered brittle and snaps instead of stretches after the elastic limit

  
• How is work done calculated in the context of springs?

  Work Done = $\frac{1}{2} kx^2$
• What is atmospheric pressure?

  The total weight of the air above a unit area at a certain altitude
• How does atmospheric pressure change with altitude?

  It decreases with increasing height above the Earth’s surface
• Why does atmospheric pressure decrease with height?

  There are fewer air molecules above the unit area at higher elevations, resulting in less weight and pressure
• What is a fluid?

  A liquid or a gas
• How does the pressure of a gas in a balloon depend on atmospheric pressure?

  The air exerts an inward force on the outer surface of the balloon
• What happens if the inward force on a balloon's surface is greater than the outward force from the gas particles inside?

  The balloon will collapse
• What occurs in space regarding atmospheric pressure and a balloon?

  There is lower atmospheric pressure, allowing the gas inside to exert a greater outward force on the balloon surface
• What happens when you blow into a balloon?

  It increases the amount of collisions the balloon surface experiences per second, raising the pressure inside
• How does pressure in a fluid act on surfaces?

  It causes a force perpendicular to any surface
• How does pressure vary with depth in a fluid?

  The deeper you are in a fluid, the greater the pressure
• Why does pressure increase with depth in a fluid?

  There is a greater amount of fluid above the object, resulting in greater weight and pressure
• How does fluid density affect pressure?

  The denser the fluid, the greater the pressure
• What is the condition for an object to float?

  An object floats if its weight is less than the weight of the water it displaces
• How does a 1000 kg boat float in water?

  It sinks until it has displaced 1000 kg of water, provided it doesn’t completely submerge
• What is the buoyancy force?

  The upwards force that counteracts the weight of the floating object
• How is the buoyancy force related to the weight of the fluid displaced by an object?

  The buoyancy force is equal to the weight of the fluid displaced by the object
• Why does a ping pong ball float on water?

  Its density is less than the density of the water, resulting in a buoyancy force greater than its weight
• How does increasing depth affect pressure in a liquid?

  Greater depth results in greater weight of the water above, leading to greater pressure
• What is the formula for pressure due to a column of liquid?

  Pressure = height of column × density of liquid × g
• What does \( g \) represent in the pressure formula?

  The acceleration due to gravity
• What does the term "buoyancy" refer to?

  The upward force exerted by a fluid on a submerged or floating object
• How does the density of an object affect its ability to float?

  If the object's density is less than the fluid's density, it will float