6.5.3 Forces and Elasticity Flashcards
Give an example of a force stretching an object.
Stretching a rubber band
Stretching a (closed) spring
Stretching a bungee cord
Give an example of forces bending an object.
Bending a ruler
Bending a straw
Give an example of compressing an object.
Compressing a shock absorber
Compressing an (open) spring
Compressing foam
How many forces need to be applied to change the shape of an object?
Two or more
Why does more than one force need to be applied to change the shape of an object?
If only one force is acting an object will move (change position) rather than change shape; the forces acting on the object must be opposing each other (acting in opposite directions.
What is elastic deformation?
This is where an object will return to its original shape once the force is removed.
What is inelastic (plastic) deformation?
This is where an object will not return to its original shape once the force is removed and has been permanently deformed.
What is Hooke’s Law in words?
The extension of an object is directly proportional to the force applied; up until the elastic limit or during elastic deformation.
What is the relationship between force, extension and the spring constant?
Force = spring constant x extension F = k e
What is the unit of the spring constant?
Newtons per metre (N/m)
Hooke’s Law applies in compression. True or false.
True
Explain what happens in terms of energy when a spring is stretched or compressed.
Work is done on the spring; the spring gains energy in the elastic/strain store.
Provided the spring does not undergo inelastic deformation, how are the work done on the spring and the elastic energy stored by the spring related?
They are equal.
What is the point where deformation changes from elastic to inelastic called?
The elastic limit.
What goes on which axis for a force extension graph?
x-axis - extension
y-axis - force
