Changes

: '''Hooke's Law''' describes how [[elastic]] [[object]]s behave when a pair of opposing [[force]]s is , one at each end of the [[object]], are applied.: '''Hooke's Law''' is described by the equation: Force = (Spring Constant ) x (Extension)

Where:: <math>F</math> = [[Equilibrium Force ]] applied: <math>k</math> = [[Spring Constant ]] (stiffness of the elastic object): <math>x</math> = [[Extension ]] of the [[object]] ===Example Calculations=======Calculating Equilibrium Force===={| class="wikitable"| style="height:20px; width:200px; text-align:center;" |A bow with a spring constant of 390N/m is stretched 0.52m. Calculate the force applied in the bow correct to two [[Significant Figures|significant figures]].| style="height:20px; width:200px; text-align:center;" |A bungee cord with a spring constant of 45N/m stretches by 29m. Calculate the [[force]] applied to the cord correct to two [[Significant Figures|significant figures]].| style="height:20px; width:200px; text-align:center;" |A slinky spring of length 15cm and spring constant 0.87N/m is stretched to a length of 10m. Calculate the [[force]] needed to stretch the slinky correct to two [[Significant Figures|significant figures]].|-| style="height:20px; width:200px; text-align:left;" |'''1. State the known quantities''' Extension = 0.52m Spring Constant = 390N/m| style="height:20px; width:200px; text-align:left;" |'''1. State the known quantities''' Extension = 29m Spring Constant = 45N/m| style="height:20px; width:200px; text-align:left;" |'''1. State the known quantities''' Original Length = 15cm = 0.15m New Length = 10m Extension = 10 - 0.15 = 9.85m Spring Constant = 0.87N/m|-| style="height:20px; width:200px; text-align:left;" |'''2. [[Substitute (Maths)|Substitute]] the numbers into the [[equation]] and [[Solve (Maths)|solve]].''' <math> F = kx </math> <math> F = 390 \times 0.52 </math> <math> F = 202.8N </math> <math> F \approx 200N </math> | style="height:20px; width:200px; text-align:left;" |'''2. [[Substitute (Maths)|Substitute]] the numbers into the [[equation]] and [[Solve (Maths)|solve]].''' <math> F = kx </math> <math> F = 45 \times 29 </math> <math> F = 1305N </math> <math> F \approx 1300N </math> | style="height:20px; width:200px; text-align:left;" |'''2. [[Substitute (Maths)|Substitute]] the numbers into the [[equation]] and [[Solve (Maths)|solve]].''' <math> F = kx </math> <math> F = 0.87 \times 9.85 </math> <math> F = 8.5695N </math> <math> F \approx 8.6N </math>|} ====Calculating Spring Constant===={| class="wikitable"| style="height:20px; width:200px; text-align:center;" |A car weighing 19000N rests on a single suspension spring. This causes the spring to shorten by 0.15m. Calculate the spring constant of this spring correct to two [[Significant Figure|significant figures]].| style="height:20px; width:200px; text-align:center;" |A girl of weight 360N balances perfectly on a pogo stick. When she is on the stick it is 13cm shorter than when she steps off. Calculate the spring constant of this spring correct to two [[Significant Figure|significant figures]].| style="height:20px; width:200px; text-align:center;" |A horse trailer of height 3.66m has 4 wheels, each with a suspension spring. When a horse which weighs 6200N gets on the trailer the height is reduced to 3.61m. Calculate the spring constant of each spring correct to two [[Significant Figure|significant figures]].|-| style="height:20px; width:200px; text-align:left;" |'''1. State the known quantities''' Extension = 0.15m Force = 19000| style="height:20px; width:200px; text-align:left;" |'''1. State the known quantities''' Extension = 13cm = 0.13m Force = 360N| style="height:20px; width:200px; text-align:left;" |'''1. State the known quantities'''Original Length = 3.66m Final Length = 3.61m Extension = 0.05m Force = 6200N|-| style="height:20px; width:200px; text-align:left;" |'''2. [[Substitute (Maths)|Substitute]] the numbers and [[Evaluate (Maths)|evaluate]].''' <math> F = kx </math> <math> 19000 = k \times 0.15 </math>| style="height:20px; width:200px; text-align:left;" |'''2. [[Substitute (Maths)|Substitute]] the numbers and [[Evaluate (Maths)|evaluate]].''' <math> F = kx </math> <math> 360 = k \times 0.13 </math> | style="height:20px; width:200px; text-align:left;" |'''2. [[Substitute (Maths)|Substitute]] the numbers and [[Evaluate (Maths)|evaluate]].''' <math> F = kx </math> <math> 6200 = k \times 0.05 </math>|-| style="height:20px; width:200px; text-align:left;" |'''3. [[Rearrange (Maths)|Rearrange]] the equation and [[Solve (Maths)|solve]].''' <math> k = \frac{19000}{0.15} </math> <math> k = 126666.7N/m </math> <math> k \approx 130000N/m </math> | style="height:20px; width:200px; text-align:left;" |'''3. [[Rearrange (Maths)|Rearrange]] the equation and [[Solve (Maths)|solve]].''' <math> k = \frac{360}{0.13} </math> <math> k = 2769.23N/m </math> <math> k \approx 2800N/m </math>| style="height:20px; width:200px; text-align:left;" |'''3. [[Rearrange (Maths)|Rearrange]] the equation and [[Solve (Maths)|solve]].''' <math> k = \frac{6200}{0.05} </math> <math> k = 124000N/m </math> <math> k \approx 120000N/m </math>|} ===References=======AQA==== :[https://www.amazon.co.uk/gp/product/019835939X/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=019835939X&linkCode=as2&tag=nrjc-21&linkId=57e96876985fc39b1a3d8a3e3dc238b6 ''Hooke’s Law, pages 13, 159, GCSE Physics; Third Edition, Oxford University Press, AQA '']:[https://www.amazon.co.uk/gp/product/0008158770/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=0008158770&linkCode=as2&tag=nrjc-21&linkId=ec31595e720e1529e49876c3866fff6e ''Hooke's Law, pages 178-9, GCSE Physics; Student Book, Collins, AQA ''] ====OCR====:[https://www.amazon.co.uk/gp/product/0198359837/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=0198359837&linkCode=as2&tag=nrjc-21&linkId=3c4229e8b023b2b60768e7ea2307cc6f ''Hooke`s law, pages 79, 253, 289, Gateway GCSE Physics, Oxford, OCR '']:[https://www.amazon.co.uk/gp/product/1782945695/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=1782945695&linkCode=as2&tag=nrjc-21&linkId=ceafcc80bcad6b6754ee97a0c7ceea53 ''Hooke’s Law, pages 170-173, Gateway GCSE Combined Science; The Revision Guide, CGP, OCR '']:[https://www.amazon.co.uk/gp/product/1782945687/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=1782945687&linkCode=as2&tag=nrjc-21&linkId=9a598e52189317a20311d7a632747bc9 ''Hooke’s Law, pages 36, 37, Gateway GCSE Physics; The Revision Guide, CGP, OCR '']