## cecekyler 3 years ago Sally applies a total force of 299 N with a rope to drag a wooden crate of mass 100 kg across a ﬂoor with a constant acceleration in the x-direction of a = 0.1 m/s 2 . The rope tied to the crate is pulled at an angle of θ = 59 ◦ relative to the ﬂoor. m Calculate the total work done by friction as the block moves a distance 21.8 m over the horizontal surface. The acceleration due to gravity is 9.8 m/s 2 . Answer in units of J

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1. furnessj

Do you need help to do it or want an answer? 3140J is what I get..

2. cecekyler

i would like how you got the answer too, apparently its really simple but i guess im just missing it

3. furnessj

I have to go for lunch, back in 30mins or so if nobody else helps before then. is the answer right..?!

4. furnessj

So, first thing is a free body diagram: |dw:1352382563028:dw|

5. furnessj

Then given the acceleration, we work out the resultant force causing that acceleration: F = ma = 100 x 0.1 = 10N Now, we find the force of friction acting against the motion: 10N = Fcos59 - F_friction, giving F_friction = 143.99N Now, the work done by this force is: Work = F_friction x distance = 143.99 x 21.8 = 3140J