Two blocks, A(50kg) and B(100kg) are connected to a string. The pulley is frictionless and of negligible mass. The coefficient of kinetic friction between block A and the incline is(adsbygoogle = window.adsbygoogle || []).push({}); Mk=0.25. Determine the change in the kinetic energy of block A as it moves from C to D, a distance of 20m up the incline if the system starts at rest.

What i did was i found Wg (work of gravitaional force), Wf (work of force) and Wff (work of frictional force) so i can use change of KE=Wg+Wf+Wff. For Wg i got -5897.79J, Wf = 19600J and Wff = -1956J. When i add these together, i got 11746.21J but the answer is suppose to be 3900J. What did i do wrong or do you guys prefer a different method.

Another question: A spring of length 080m rests along a frictionless 30degree incline. A 2.0kg mass, at rest against the end of the spring, compresses the spring by 0.10m. A) Determine the spring constantk. B) The mass is pushed down, compressing the spring an addtional 0.60m, and then released. If the incline is 2.0m long, determine how far beyond the rightmost edge of the incline the mass lands.

If someone could show me the steps to these problems, it would be greatly appreciated. Thanks!!

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# Homework Help: Need help with work and energy

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