Posted by **Becca** on Tuesday, December 5, 2006 at 5:28pm.

A 70.0 kg base runner begins his slide into second base while moving at a speed of 4.0 m/s. The coefficient of friction between his clothes and Earth is .70. He slides so that his speed is zero just as he reaches the base. How much mechanical energy is lost due to friction acting on the runner.

I know the equation I have to use is KE_i - PE_f = delta ME, but I don't know how to use the coefficient of friction in those equations.

All of the KE is lost due to friction. He had ke, now he has zero ke. Conclusion: all of the KE is dissipated in friction. The coefficent of friction is not needed for this part.

so the mechanical energy lost is just how much kinetic energy there was in the beginning?

I also need to find how far he slides, and the only equation that doesn't use time is vf^2=(vi)^2+2a*x, and I don't know acceleration either. What equation works?

Ok, you know the average force*distance=KE lost.

but force= mg*mu

solve for distance.

- Physics -
**Jill**, Sunday, January 13, 2013 at 2:15pm
a. -560 J

b. d = 1.2 m

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