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How much work must be done to stop a 1175 kg car traveling at 125 km/h?

Sagot :

According to Work energy theorem,

[tex]W=\frac{1}{2}mv^2-\frac{1}{2}mu^{2^{}^{}}^{}[/tex]

Finally, the car comes at rest therefore,

[tex]v=0\text{ m/s}[/tex]

Substitute the given value in the equation of work-energy theorem,

[tex]\begin{gathered} W=\frac{1}{2}(1175kg)(0m/s)^2(\frac{1\text{ J}}{1kgm^2s^{-2}})-\frac{1}{2}(1175\text{ kg)(}125km/h)^2(\frac{1000\text{ m}}{1\text{ km}})^2(\frac{1\text{ h}}{60\text{ min}})^2(\frac{1\text{ min}}{60\text{ s}})^2(\frac{1\text{ J}}{1kgm^2s^{-2}}) \\ =0\text{ J-}708309\text{ J} \\ =-708309\text{ J} \end{gathered}[/tex]

Thus, the magnitude of work done to stop the car is 708309 J.