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# Power energy calculation watch

1. I have the following question which I need guidance on part B.

Q5A) A crate containing 40 bricks is raised by a forklift through a height of 1.3m to place on a truck bed. Determine the potential energy gained by the crate if each brick has a mass of 1.3kg.

Answer: PE=mxgxh (40x1.3) 52kg x 9.81 x 1.3 = 663.16J

Q5B) The crate is then pulled by a hoist a distance of 3.4m across the flat bed in 8 seconds. Determine the work done in moving the crate and the power of the hoist when the coefficient of friction is 0.6

work done=friction x distance 663.16J x 3.4?
2. work done = friction * distance... but the friction is not the PE

to find the friction you need to work out the normal reaction force R and multiply it by the coefficient of friction μ
3. Would that be 510N x 0.6 = 306?

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Updated: December 31, 2012
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