A LEVEL PHYSICS Year 1 Stress and Strain Review and Elastic Energy A* A B C Be able to calculate the elastic strain energy stored in a stretched material using the area under a force extension graph or the formula. Understand how energy is conserved in B/C
Target A/A* Target EP EP EP EP AEP EP
If you increase the force past the elastic limit the material will become permanently stretched. Materials obey Hookes law up to the limit of proportionality/Hookes law limit. It is the point beyond which the force is not proportional to the extension. If a deformation is elastic the material returns to its original shape after all force is removed. Metal deformation is elastic when it obeys Hookes law. If a deformation is plastic the material is permanently deformed after all force is removed.
Not just plastic materials! The atoms do not return to their original equilibrium position. Tensile Stress Breaking Stress: A stress that is big enough to break the materials apart (tears the atoms apart from each other). Ultimate Tensile Stress: The maximum stress a material can withstand
Tensile Strain Elastic Strain Energy Work has to be done to stretch a material. Before the elastic limit all this work done is stored as potential energy. This stored energy is called elastic strain energy. Calculating energy stored Deriving the formula The energy stored is equal to the work done. W = F x d = ( F) x d = ( F) x L The force is not constant so you need to take the average from 0 to F. So the elastic strain energy is: E = F L
Because the material obeys Hookes Law (F = kL), F can be replaced in the equation. E = F L = k L L = k L2 In the exam you may be 2 E = k L asked to derive this formula from the graph. Conservation of Energy When the stretching force is removed after an elastic deformation the stored energy is transferred to other forms (elastic band fires across a room). If the deformation is plastic work is done to separate atoms therefore energy is not stored as strain energy, it is dissipated as heat. Gravitational
potential energy In reality there is always some energy transferred as heat but you can usually ignore this in conservation calculations. Kinetic energy Elastic strain energy Conservation of Energy When the stretching force is removed after an elastic deformation the stored energy is transferred to other forms
(elastic band fires across a room). If the deformation is plastic work is done to separate atoms therefore energy is not stored as strain energy, it is dissipated as heat. Therefore, Change in kinetic energy = Change in potential energy Both elastic strain energy and gravitational potential energy Energy Conservation in Transport Design (again) Modern cars must have crumple zones that deform plastically in a collision. The cars kinetic energy goes into changing the shape of the vehicle, so less is transferred to passengers.
In trains this has to be balanced with the fact that the driver has to sit at the front Practice Questions A/A*Target Qs.3-6 Pg.178 Q.1 & 2 Pg.187 B/C Target Qs.1-6 Pg.178 Q.1 Pg.187
Rationale. DepEd continues to work towards making all schools child-friendly, safe and conducive to learning. Part of this effort is providing the appropriate facilities for each school based on data collected from our schools and standards set by policymakers.
Which word is an antonym for grouchy? angry greedy cheerful lively mean. For SOL 3.4b, the student performance data indicate that students appear to be challenged by the use of antonyms, not synonyms. Sometimes, the test question will include a...
Office of US Congressman Darrell Issa (CA) Utilization Tour: Special Assistant to Secretary of the Navy for Manpower and Reserve Affairs Wounded Warrior Care and Transition Policy(WWCTP) 2011 Senate Fellow. Master Sergeant Julius D. Spain Sr. Office of United States...
HS ELAR Notes: Have KWL note-taking sheet with K filled in- Sort samples of differentiation by how often principals see it in ELAR classrooms. Using "routinely" category, determine what "type" of differentiation teachers are best at.
Style-figurative language. Imaginative use of words to express ideas that are not literally true, but are meaningful and can have an emotional impact to show meaning and feeling -or tone in the narrative.. Simile "The leading edge of the storm...