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A-lorry-goes-round-an-unbanked-curve-If-the-radius-of-the-curve-is-30m-and-the-coefficient-of-friction-between-the-ground-and-the-tyre-is-0-6-Calculate-the-maximum-speed-of-the-lorry-g-10m-s-2-




Question Number 24177 by NECx last updated on 13/Nov/17
A lorry goes round an unbanked  curve.If the radius of the curve  is 30m and the coefficient of  friction between the ground and  the tyre is 0.6. Calculate the  maximum speed of the lorry.  (g=10m/s^2 )      please buddies help
Alorrygoesroundanunbankedcurve.Iftheradiusofthecurveis30mandthecoefficientoffrictionbetweenthegroundandthetyreis0.6.Calculatethemaximumspeedofthelorry.(g=10m/s2)pleasebuddieshelp
Commented by NECx last updated on 14/Nov/17
please help
pleasehelp
Answered by mrW1 last updated on 14/Nov/17
((mv^2 )/r)≤μmg  ⇒v≤(√(μgr))=(√(0.6×10×30))=13.4 m/m=48 km/h
mv2rμmgvμgr=0.6×10×30=13.4m/m=48km/h
Commented by NECx last updated on 14/Nov/17
but I thought that the centripetal  force was going to be greater than  the frictional or equal not less   because it is already in motion  thus overcoming the frictional  force.    Please explain why ((mv^2 )/r)≤μmg
butIthoughtthatthecentripetalforcewasgoingtobegreaterthanthefrictionalorequalnotlessbecauseitisalreadyinmotionthusovercomingthefrictionalforce.Pleaseexplainwhymv2rμmg
Commented by mrW1 last updated on 14/Nov/17
The centripetal force ((mv^2 )/2) is   provided by the friction force f,  and the friction force f may not  be more than μmg, thus  ((mv^2 )/2)≤μmg
Thecentripetalforcemv22isprovidedbythefrictionforcef,andthefrictionforcefmaynotbemorethanμmg,thusmv22μmg
Commented by NECx last updated on 15/Nov/17
I now understand.... Thanks sir.
Inowunderstand.Thankssir.
Answered by ajfour last updated on 14/Nov/17
μmg = mv^2 /r  ⇒  v =(√(μgr))             =(√(0.6×10×30)) =6(√5) m/s .
μmg=mv2/rv=μgr=0.6×10×30=65m/s.

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