Hookes' Law, Force and Extension

1. 1Hookes' Law:
   - An object obeys Hookes' Law if the e[blank_start]xtension[blank_end] or c[blank_start]ompression[blank_end] (Δx) of the object is [blank_start]directly[blank_end] [blank_start]proportional[blank_end] to the l[blank_start]oad[blank_end] or f[blank_start]orce[blank_end] applied to it (ΔF), up to the [blank_start]limit[blank_end] [blank_start]of[blank_end] [blank_start]proportionality[blank_end].
   - A force-extension graph for an object obeying Hookes' Law is a [blank_start]straight[blank_end] [blank_start]line[blank_end] through the [blank_start]origin[blank_end].
   - Hookes' Law applies to an object rather than to a [blank_start]material[blank_end].
   - Hookes' Law can be written as Δ[blank_start]F[blank_end] = [blank_start]k[blank_end]Δ[blank_start]x[blank_end] where k is the s[blank_start]tiffness[blank_end] of the object that is being stretched. k is called the f[blank_start]orce[blank_end] constant (or stiffness constant) and has units [blank_start]Nm^-1[blank_end].
   - The object will only deform if there's a p[blank_start]air[blank_end] of o[blank_start]pposite[blank_end] forces acting on it.

   

   1. Axtension
   2. Bompression
   3. Cdirectly
   4. Dproportional
   5. Eoad
   6. Force
   7. Glimit
   8. Hof
   9. Iproportionality
   10. Jstraight
   11. Kline
   12. Lorigin
   13. Mmaterial
   14. NF
   15. Ok
   16. Px
   17. Qorce
   18. RNm^-1
   19. Stiffness
   20. Tair
   21. Upposite
2. 2Springs and Hookes' Law:
   - The extension or compression of a spring is [blank_start]directly[blank_end] [blank_start]proportional[blank_end] to the [blank_start]force[blank_end] applied up until the limit of proportionality so [blank_start]Hookes'[blank_end] [blank_start]Law[blank_end] applies.
   - For springs, k in the formula ΔF = kΔx can also be called the spring s[blank_start]tiffness[blank_end] or spring c[blank_start]onstant[blank_end].
   - Tensile or compressive forces in a spring act in the [blank_start]opposite[blank_end] direction to the tensile or compressive forces stretching or squashing it.
   - Springs in [blank_start]parallel[blank_end]: 2 or more springs connected side-to-side from the same end fixtures. If multiple springs are in parallel, the force in each of the springs is [blank_start]halved[blank_end] for 2 springs so overall [blank_start]extension[blank_end] is halved for 2 springs, etc.
   - Springs in [blank_start]series[blank_end]: 2 or more springs connected end-to-end. If multiple springs are in series, the force in each of the springs is [blank_start]the[blank_end] [blank_start]same[blank_end] so the overall extension is [blank_start]double[blank_end] for 2 springs, [blank_start]triple[blank_end] for 3, etc.

   

   1. Adirectly
   2. Bproportional
   3. Cforce
   4. DHookes'
   5. ELaw
   6. Ftiffness
   7. Gonstant
   8. Hopposite
   9. Iparallel
   10. Jseries
   11. Khalved
   12. Lextension
   13. Mthe
   14. Nsame
   15. Odoubled
   16. Ptripled
3. 3If a metal wire is supported at the [blank_start]top[blank_end] and then a [blank_start]weight[blank_end] attached to the bottom, it [blank_start]stretches[blank_end]. The weight pulls down with force [blank_start]w[blank_end], producing an [blank_start]equal and opposite[blank_end] force of w at the [blank_start]support[blank_end]. Therefore there are a [blank_start]pair of opposite forces[blank_end] acting which cause an [blank_start]extension[blank_end] so [blank_start]Hookes' Law[blank_end] can apply.

   

   1. Atop
   2. Bweight
   3. Cstretches
   4. Dw
   5. Eequal and opposite
   6. Fsupport
   7. Gpair of opposite forces
   8. Hextension
   9. IHookes' Law
4. 4Spring/Force/Stiffness Constant (k):
   - The [blank_start]constant[blank_end] [blank_start]of[blank_end] [blank_start]proportionality[blank_end] which relates force and extension or force and compression for an object which obeys [blank_start]Hookes'[blank_end] [blank_start]Law[blank_end].
   - It has symbol [blank_start]k[blank_end] and units [blank_start]Nm^-1[blank_end].
   - The [blank_start]higher[blank_end] an object's spring constant, the more [blank_start]force[blank_end] that is required to d[blank_start]eform[blank_end] it by a given amount.
   - The spring constant of an object is equal to the [blank_start]gradient[blank_end] of a force-e[blank_start]xtension[blank_end] or force-c[blank_start]ompression[blank_end] graph (the [blank_start]straight[blank_end] line part).
   - The spring constant of an object depends on its s[blank_start]hape[blank_end] as well as the [blank_start]material[blank_end] the object is made from.

   

   1. Aconstant
   2. Bof
   3. Cproportionality
   4. DHookes'
   5. ELaw
   6. Fk
   7. GNm^-1
   8. Hhigher
   9. Iforce
   10. Jgradient
   11. Kxtension
   12. Lompression
   13. Mstraight
   14. Nmaterial
   15. Oeform
   16. Phape
5. 5What does each point on the graph represent?

   

   1. ALimit of proportionality
   2. BElastic limit
   3. CYield point
   4. DBreaking force
   5. EWire breaks
   6. FUnloading curve parallel to LOP line
6. 6Points on a Force-Extension Graph:
   1. [blank_start]Limit of proportionality[blank_end] - the point beyond which the [blank_start]extension or compression[blank_end] of a loaded object or material is no longer [blank_start]directly proportional[blank_end] to the force (i.e. point beyond which Hookes' Law is no longer obeyed if graph started at the [blank_start]origin[blank_end]). Also the end of the [blank_start]straight line[blank_end] part of the graph.
   2. [blank_start]Elastic limit[blank_end] - the point beyond which a material or specimen is [blank_start]plastically[blank_end] deformed when it is being loaded (i.e. the point beyond which it does not return to its original dimensions when the load is removed thus being [blank_start]permanently deformed[blank_end]).
   3. [blank_start]Yield point[blank_end] - the point beyond which the material undergoes a [blank_start]large increase in extension[blank_end] with [blank_start]little extra load[blank_end]. It usually occurs at deformations a little beyond [blank_start]the elastic limit[blank_end]. It marks the point at which, the [blank_start]internal microscopic structure[blank_end] of the material starts to become re-organised.
   4. [blank_start]Breaking force[blank_end] - the maximum [blank_start]force[blank_end] a material can take before it breaks.
   5. [blank_start]Breaking point[blank_end] - the point at which the object [blank_start]breaks[blank_end].
   6. [blank_start]Unloading curve/line[blank_end] - [blank_start]parallel[blank_end] to the straight line part of the graph. Where it [blank_start]intercepts[blank_end] the extension axis shows the [blank_start]permanent extension[blank_end] of the object/material (i.e. back to the origin means the object behaves [blank_start]elastically[blank_end] so suffers [blank_start]no[blank_end] permanent extension).

   

   1. ALimit of proportionality
   2. BUnloading curve/line
   3. CBreaking force
   4. DBreaking point
   5. EYield point
   6. FElastic limit
   7. Gdirectly proportional
   8. Horigin
   9. Istraight line
   10. Jextension or compression
   11. Kplastically
   12. Lpermanently deformed
   13. Mlarge increase in extension
   14. Nlittle extra load
   15. Othe elastic limit
   16. Pinternal microscopic structure
   17. Qforce
   18. Rbreaks
   19. Sparallel
   20. Tintercepts
   21. Upermanent extension
   22. Velastically
   23. Wno
7. 7A Deformation can be Elastic or Plastic:
   A material will show [blank_start]elastic[blank_end] deformation up to its elastic limit, and [blank_start]plastic[blank_end] deformation beyond it.
   - If a deformation is elastic, the material returns to its [blank_start]original[blank_end] shape once the forces are removed.
   - When the material is put under t[blank_start]ension[blank_end], the atoms of the material are [blank_start]pulled[blank_end] apart from one another. Atoms can move slightly relative to their [blank_start]equilibrium[blank_end] positions, without changing p[blank_start]osition[blank_end] in the material. Once the load is removed, the atoms [blank_start]return[blank_end] to their equilibrium distance apart.
   - If a deformation is plastic, the material is [blank_start]permanently[blank_end] stretched.
   - Some atoms in the material [blank_start]move[blank_end] position relative to one another. When the load is removed, the atoms [blank_start]don't[blank_end] return to their original positions.

   

   1. Aelastic
   2. Bplastic
   3. Coriginal
   4. Dpulled
   5. Eequilibrium
   6. Freturn
   7. Gpermanently
   8. Hmove
   9. Idon't
   10. Josition
   11. Kension
8. 8Compression:
   - A type of force which acts w[blank_start]ithin[blank_end] an object or material to [blank_start]squash[blank_end]/shorten the object or material.
   - It can be used to mean a d[blank_start]ecrease[blank_end] in the size of a material sample when a [blank_start]compressive[blank_end] force is applied to it.
   - Compression is sometimes called compressive d[blank_start]eformation[blank_end].

   

   1. Asquash
   2. Bcompressive
   3. Ceformation
   4. Dithin
   5. Eecrease
9. 9Tension:
   - A force acting w[blank_start]ithin[blank_end] an object or material in a direction that would e[blank_start]xtend[blank_end] the object or material.
   - Extension is sometimes called tensile d[blank_start]eformation[blank_end].

   

   1. Aithin
   2. Bxtend
   3. Ceformation
10. 10The more flexible a material, the more it can bend without breaking.

    1. ATrue
    2. BFalse

11. 11You can draw an unloading line on a force-extension graph of an object which experiences enough load to fracture it.

    

    1. ATrue
    2. BFalse
12. 12Unloading Lines/Curves:
    - When the load is removed, [blank_start]extension[blank_end] decreases.
    - The unloading line is [blank_start]parallel[blank_end] to the loading line because the [blank_start]stiffness[blank_end] constant k is still the same (since the forces between the atoms are [blank_start]the same[blank_end] as they were during the loading).
    - If the object is stretched beyond its [blank_start]elastic limit[blank_end] it deforms plastically and is [blank_start]permanently[blank_end] stretched. This means the unloading line doesn't go through the [blank_start]origin[blank_end].
    - The [blank_start]area[blank_end] between the two lines is the [blank_start]work done to permanently deform the wire[blank_end].

    

    1. Aextension
    2. Bparallel
    3. Cstiffness
    4. Dthe same
    5. Eelastic limit
    6. Fpermanently
    7. Gorigin
    8. Harea
    9. Iwork done to permanently deform the wire

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AS - Level Sally's Physics (Materials) Quiz on Hookes' Law, Force and Extension, created by Sally Lancaster on 12/03/2016.

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Sally Lancaster

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