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Find the average frictional force needed to stop a car weighing 500 kg in a distance of 25 m if the initial speed is 72 km/h. |
Answer» Here, `F=?, m=500kg, s=25m, v=0, u=72km//h=(72xx1000)/(60xx60)m//s=20m//s` According to word energy principle, `W =`change of K.E. of the body `Fs=(1)/(2)m(v^(2)-u^(2))` `Fxx25=(1)/(2)xx500(0-20^(2))=-(500xx400)/(2)` `F=(500xx200)/(25)=-4000N :.` Average frictional force `=400N` |
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