Help
Options
Didn't know it?
click below
click below
Knew it?
click below
click below
Don't Know
Remaining cards (0)
Know
retry
shuffle
restart
0:00
Embed Code - If you would like this activity on your web page, copy the script below and paste it into your web page.
Normal Size Small Size show me how
Normal Size Small Size show me how
Physics Materials
Physics Spring Y12
| Question | Answer |
|---|---|
| Hooke's Law definition | An object obeys Hooke's law if the force applied is directly proportional to its extension up to the ELASTIC LIMIT |
| Tensile deformation | Where forces extend a material |
| Compressive deformation | Were forces compress a material |
| Graph for spring under tension | Directly proportional until elastic limit, where it then curves flatter. When force is removed, it goes diagonally back (looks same gradient as original proportional section. dotted line) |
| What happens to spring extension after force removed | If the spring is stretched to A, when the force is removed it will not return to its original length as it is plasticly deformed |
| Elastic deformation definition | The material will return to its original length/shape when the force is removed |
| Plastic deformation definition | The material will not return to its original length/shape when the force is removed |
| Springs added together | Refer to in terms of parallel/series |
| Parallel springs identical | Each spring has F/2 So each spring has half extension = 4.7mm We look at the whole system: k = F/e = 58.4 N/m In parallel kn (combined k) = nk |
| Series springs identical | Each spring receives the full force etc In series kn (combined k) = k/n |
| Springs non-identical | P: k = k1 + k2 + k3 S: 1/k = 1/k1 + 1/k2 + 1/k3 Flipped from electrical circuits |
| Elastic material stretched then released on graph back to original shape. How to calc energy dissipated | Area between 2 lines returning |
| Proof for EPE (is on the back of one of the physics books if this terrible explanation doesnt work) | Consider spring stretched from natural length to extension, x. Force = F(x) [force is a function of x] F(x) = kx W = ∫F(x) dx = Ep Ep = x over 0 ∫kx' dx' = [0.5kx'^2] x over 0 =0.5k x^2 <--- Using F=kx Ep = 0.5Fx |
| How fast will a spring be travelling once fully extended after being pressed then released | Assuming conservation of energy, Ep = 0.5 mv^2 |
| Spring constant is dependent on | Object shape (thickness like parallel, length like series) Young's Modulus is intrinsic to the material and independent of shape |
| Tensile stress symbol and meaning | Lower case sigma Stress accounts for the thickness Pascals (= Nm^-2) |
| Tensile strain symbol and meaning | Epsilon No unit (ratio) or as a % |
| Young's Modulus unit | Also Nm^-2 (pascals), showing stress is def on the top or it would be N^-1 * m^2 |
| Young's Modulus rough magnitude | Normally in 10^9 to 10^12 |
| Stress rough magnitude | Normally in millions |
| What to check for in stress questions | Area vs diameter Diameter vs radius |
| Limit of proportionality definition | Point beyond which stress is no longer proportional to strain |
| Elastic limit definition | Beyond which it does not return to its original shape when force removed |
| Yield point(s) definition | The point at which there is a large increase in the strain for small increases in stress |
| Ultimate tensile strength definition | The maximum stress that a material can experience without breaking |
| Breaking strength definition | The stress at which the material will break |
| Ductile definition | A ductile material can be easily drawn out into wires or hammered into sheets (i.e. can undergo larger strains) |
| Brittle definition | A brittle material breaks at low strain i.e. does not yield |
| Polymeric definition | Consist of long molecular chains (polymers), they have a range of behaviours |
| Stress on y axis strain on x axis Difference between brittle/ductile | Brittle strong (e.g. cast iron) is steep straight line, with weak (e.g. glass) being flatter (often flatter than ductile). Ductile is a curve that decreases in gradient |
| Mild steel stress strain graph | Starts straight line diagonal, then curves off (first P, then E, then Y1 at the very peak), sinking down a bit to a minimum (Y2), then a wider curve that peaks at UTS then sinks down a bit to B |
| Rubber stress strain graph | High, then low, then high gradient, then the opposite going back. Use arrows to show which is which (going back is the lower one) |
| Polythene stress strain graph | Straight line diagonal, then curves off into a straight line going slightly diagonally up but mostly flat. Then dotted (once force removed) line going down at a less steep way than the first line |
| Graph with diagonal line not through origin where gradient represents spring constant. What are the axis titles | Force on y. LENGTH on x, not extension if it doesn’t go through origin |
| Setup in lab with 2 springs on platform connected to rod. How to measure spring constant | Use newtonmetre to measure force pulling, with ruler for extension |
| For a setup with multiple springs, when measuring spring constant from graph | Divide by number of springs if they’re asking for a single spring |
| When describing Young’s modulus even slightly related to a graph | Mention it’s the gradient of a stress-strain graph |
| To shape a spring or wire, what forces are required? | PAIR of *equal and opposite* forces required. i.e. tension and NCF or two tensions Same for compressing |
| Name for the shape of the curve on an Fx graph for rubber | hysteresis loop Rubber does not experience plastic deformation, but it does not obey Hooke’s law |
| Polyethene | Polyethene is a polymeric material. It does not obey Hooke’s law, and experiences plastic deformation when any force is applied to it. This makes it very easy to stretch in to new shapes. |
| Attaching masses in an experiment | Say is doing a force of mg |
| Measuring with fiducial marker | reading the values for the extension at eye-level and using a set square to make sure the ruler is straight |
| Phrasing energy transfer | Work is done as energy from X to Y |
| Plastic deformation | If plastic deformation occurs, then the work done to achieve this deformation is not stored as elastic potential energy, it is used to rearrange the atoms in to their new permanent positions. |
| Young's modulus experiment basic reminder | Wire clamped to table. Fiducial marker. Wire over pulley. Measure diameter at multiple points. Apply weights. Etc |
| Phrasing for brittle materials | no plastic deformation, and the loading and unloading curve are the same |
| Phrasing for elastic materials | An elastic material such as rubber can endure a lot of tensile stress before breaking. There is no plastic deformation, but the unloading curve is different to the loading curve, as some energy has been lost as thermal energy. |
| Why polymeric materials have the graph shape they do (like polyethene. rubber also polymeric but the graph we look at for it only does elastic deformation) | Untangling, stretching, breaking |
Created by:
Pyrogearos2