Forces And Elasticity Flashcards
What does stretching, compressing and bending an object require?
More than one force (at least 2) acting on the object otherwise the object would move in one direction of the applied force instead of changing shape.
What are elastically distorted objects?
Those which can go back to their original shape and length after the force has been removed (elastic objects)
What are inelastic ally distorted objects?
Objects that don’t return to their original shape and length after the force has been removed
What is the elastic limit?
The point where an object stops distorting elastically and begins to distort inelastically
Stops acting elastically
What happens when a force stretches or compresses an object?
-work is done causing an object’s energy to be transferred to the elastic potential energy store of the object. If it elastically distorted ALL the energy is transferred
What is hooke’s law that applies to elasticity?
Force is directly proportional to extension up to the elastic limit
-this means there is a linear relationship between force and extension (straight line on a graph)
F = KX (K=spring constant, X is extension, F is the force)
-X can also act for compression (difference between natural and compressed length)
What is the spring constant!?
A property of all stretched objects that measures how many Newton’s it takes to stretch something a meter
-every material has its own unique one
What happens when an object is stretched too much?
Extension becomes no longer proportional to force (non-linear) as the object stretches more for each unit increase of force. This point is known as the limit of proportionality where it stops obeying hookes law
How do you calculate work done for linear relationships?
As long as a spring isn’t stretched past it’s limit if proportionality, work done to the spring equals the energy stored in the elastic potential energy store
E = 0.5 x K x X squared or E = 0.5 x F x X (X must be in meters)
-you could also work out the areas under the linear section of your force extension graph
What are stages 1 and 2 of investigating elasticity?
- measure the natural length of the spring it’s a millimetre tiler clamped to the stand
- add a mass to the spring and allow it to come to rest, record the mass and measure the new length of the spring, extension is change in length
What are stages 3 and 4 of measuring elasticity?
- repeat to gather enough measurements varying the mass each time and keeping the same identical spring
- plot a force extension graph, it should only start to curve if you exceed the limit of proportionality
