5.3 Forces & Elasticity

• What must happen for stationary objects to change shape?

  More than one force must be applied
• How can the shape of an object change?

  By stretching, bending, or compressing
• What is stretching in terms of forces?

  Forces in opposite directions away from the object
• What is bending in terms of forces?

  Forces that distort the object
• What is compressing in terms of forces?

  Forces in opposite directions towards the object
• Can a combination of shape changes occur?

  Yes, all three shape changes can occur
• What are the two forces acting on a spring during compression?

  The weight of the mass and the reaction force

  
• How do the forces act during compression?

  They act towards each other
• What are the two forces acting on a spring during stretching?

  The weight of the mass and the tension in the spring

  
• How do the forces act during stretching?

  They act away from each other
• What are the two forces acting on a diving board when bending?

  The weight of the swimmer and the reaction force

  
• How do the forces act during bending?

  They act towards each other at different points
• Can bending be caused by forces at an angle?

  Yes, forces at an angle can cause bending
• What is elastic deformation?

  When objects return to their original shape after stretching

  
• What materials undergo elastic deformation?

  Rubber bands, fabrics, and steel springs
• What is inelastic deformation?

  When objects remain stretched and do not return to original shape

  
• What materials undergo inelastic deformation?

  Plastic, clay, and glass
• What does Hooke's Law define?

  The relationship between extension and applied force

  
• What does Hooke's Law state?

  Extension is directly proportional to the force applied

  
• What happens if the force is doubled according to Hooke's Law?

  The extension will also double

  
• What is the limit of proportionality?

  The point beyond which force and extension are not proportional

  
• What is the equation for Hooke's Law?

  F = k × e

  
• What does the symbol F represent in Hooke's Law?

  Force in newtons (N)
• What does the symbol k represent in Hooke's Law?

  Spring constant in newtons per metres (N/m)

  
• What does the symbol e represent in Hooke's Law?

  Extension in metres (m)

  
• What does the spring constant indicate?

  How stiff a spring is
• How is the extension of an object calculated?

  Final length – original length
• How is the extension of a spring measured?

  By marking the position of the unstretched spring
• What is the significance of the gradient on a force-extension graph?

  It represents the spring constant

  
• What does a straight line on a force-extension graph indicate?

  Material obeys Hooke's law

  
• What does a curve on a force-extension graph indicate?

  Material does not obey Hooke's law

  
• What does the symbol Δ represent in equations?

  'Change in' a variable
• What does the symbol '∝' mean?

  'Proportional to'
• What does a steep straight line on a force-extension graph indicate?

  Material has a large spring constant

  
• What does a shallow straight line on a force-extension graph indicate?

  Material has a small spring constant

  
• What is the relationship between force and extension in Hooke's law region?

  They are directly proportional

  
• How can the spring constant be calculated?

  By rearranging Hooke's law equation for k

  
• What does the spring constant indicate about a spring?

  More force is needed per unit extension

  
• What is the formula for calculating elastic potential energy?

  Not provided in the material

  
• What is the extension of the pogo stick spring?

  7 cm