# Energy & Work Problems

1. Jan 6, 2010

### dagitt

1. The problem statement, all variables and given/known data
1. A 10.5 m long conveyor belt, inclined at 30.0°, is used to transport bundles of newspapers from the mailroom up to the cargo bay to be loaded on to delivery trucks. Each newspaper has a mass of 1.0 kg, and there are 28 newspapers per bundle. Determine the power that the conveyor develops if it delivers 15 bundles per minute.

2. Use the graph in the diagram

to find the work needed to stretch the spring from 0.14 m to 0.26 m.

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any or all help appreciated...THANKS SO MUCH <33

2. Relevant equations
For both 1 & 2...
basic trig, W=F*d, P = change in W / Change in T, KE = .5mv^2, PE = mgh (but I'm confused if I even need KE or PE to solve these...?)

3. The attempt at a solution
For 1, I drew out the ramp and all the force components. I determined the force per bundle to be 137.2 N per bundle, and the total Work to be 1440.6...I multiplied this by 15, to get the answer, but it wasn't correct...I'm just so confused as to how to approach this.

2. I added the change in force at those two points, and multiplied it by distance traveled which is .26 - .14 m. Got this wrong too...

any or all help appreciated. i suck at physics. thanks so much.

2. Jan 6, 2010

### JaWiB

For #1, are the units in your final answer correct? I assume they want it in Watts (J/s)

For #2, I'm not sure I understand what you are doing. What do you mean by "change in force at those two points"?

3. Jan 6, 2010

### ideasrule

This looks right to me.
Work done is just the area under the graph, since W=Fd for constant F and d, and the graph can be broken down into an infinite number of infinitely thin rectangular tiles each with constant F and d.

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