How much work must be done to stop a 980 kg car traveling at 108 km/h?(adsbygoogle = window.adsbygoogle || []).push({});

what i did was first convert the km/h to m/s:

[tex]108 * 1000 / 3600 = 30[/tex]

then plug the mass and velocity into the kinetic energy forumula [tex]K.E. = \frac{1}{2} mv^2[/tex]

[tex] \frac{1}{2}980(30^2) = 441000 [/tex]

I have checked and rechecked it and i keep coming up with that answer but its wrong. Where am I going wrong or is there more to do?

Another problem i need help with is this:

At an accident scene on a level road, investigators measure a car's skid mark to be 88 m long. It was a rainy day and the coefficient of friction was estimated to be 0.46. Use these data to determine the speed of the car when the driver slammed on (and locked) the brakes.

I don't even know where to get started on this one especially without a mass, but my teacher says the mass doesnt matter.

Any help on these would be greatly appreciated.

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# Homework Help: How much work must be done to stop a 980 kg car traveling at 108 km/h?

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