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A Level Physics Solid Materials Hooke s Objectives 53 be able to use the Hooke s law equation F k x where k isthe stiffness of the object.

54 understand how to use the relationships tensile compressive stress force cross sectional area tensile compressive strain change in length original length Young modulus stress strainAdditional skills gained .

Calculating the gradient of a graphical representation Identifying the value of the stiffness constant k Starter Number RiddleThere is one 5 digit number that whenmultiplied by 4 gives you the opposite.

of your original number e g 12345 54321 You have 10mins ONLY Whenever a force acts on a material Context the materials will be deformed into a.

different size or shape If a material is made longer then the force is referred to astension and the extra length is known as extensionIf a material is shortened then the force is referred to ascompression and the reduced size is known as negative.

Force AppliedIf a material is elastic it will deform with application of a loadbut will return to its original dimensionsIf a material is plastic it will remain deformed Robert Hooke.

Robert Hooke was an outstandingscientist who was well known for being arival to his peer Isaac Newton One of his least noticeable achievements he discovered the cell was his work on.

the physical properties of a springHooke s law states that the force needed to extend a spring isproportional to the extension of the spring UNTIL the limit ofproportionality has been reachedForce applied N Stiffness constant Nm 1 x Extension m .

Practice QuestionA spring has a stiffness constantof 50Nm 1 and is 3cm longnaturally What will be its newlength when a 200g mass is.

hung from it Hooke s Law You can do a simple experiment tocalculate the stiffness constant of aPractical spring Set up in pairs the equipment.

shown on the left hand side You will be loading more andmore mass 0g 700g recordingboth the original length and theloaded length.

Calculate the extension andrecord it in meters If you plot your dependentvariable extension on the x axis you can calculate the value for k.

by working out the gradient of NOTE line of best fit should gothrough 0 0 The inherent quality of aDefinition Match material that determines the.

proportionality between anapplied force and extensionLimit of proportionality The maximum extension that amaterial can exhibit that is stillElastic Limit proportional to the load applied.

Yield Point The point at which the materialwill elongate without any extraadded load acts plastically Stiffness ConstantThe maximum extension that a.

material can undergo and stillreturn to its original dimensionswhen the load is removed Elastic Strain The work done in deforming a material beforeit reaches the elastic limit will be stored.

internally asEnergy elastic strain energy Eel Previously we learned an equation tocalculate the work done by a force whichWork done Force x Distance in direction.

This is true also for deformations but asHooke s law shows the force varies withdifferent extensions so to calculate thework done we need to use the averageforce over the distance of extension.

E el F A K A The areaunder the graph Practice QuestionsCalculate the total work done inloading the spring in your.

experiment to its limit ofproportionalityWhat is the spring constant for aspring that starts at a length of25cm and extends to a length of.

32cm when a mass of 50g is Material TermsUse pages 190 191 and 205 table to completenotes on terms used when describing solidmaterials .

Objectives 53 be able to use the Hooke s law equation F k x where k isthe stiffness of the object54 understand how to use the relationships tensile compressive stress force cross sectional area.

tensile compressive strain change in length original length Young modulus stress strainAdditional skills gained Calculating the gradient of a graphical representation Identifying the value of the stiffness constant k .

Hookeâ€™s law . states that the force needed to extend a spring is . proportional. to the extension of the spring UNTIL the . limit of proportionality . has been reached. Force applied (N) = Stiffness constant (Nm-1) x Extension (m) âˆ†ð¹=ð‘˜ âˆ†ð‘¥

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