Calculate the work required to move the block

kuruman

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Friction is a horizontal force. I'm assuming friction would be the floor on block, floor on man?
Yes. Let's do first "floor on block". The relevant expression is Friction = Ffloor on block, x = μ Ffloor on block, y. Do you see how it works? So, what do you need to find the force of friction?
I'm really lost as to what I'm even trying to figure out now.
Please answer my last question in B, in post #23. Then you will see better what's going on.

haruspex

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friction would be the floor on block, floor on man?
You need to distinguish between kinetic and static friction. Which of those describes the friction between the floor and the man?
The surfaces in static friction do not move relative to each other, so static friction does no work.

kuruman

Homework Helper
Gold Member
For some reason, I feel this isn't right?
Work done on a system is done by forces external to the system. The system cannot do work on itself. In this case if the system is block, then one has to consider the works done by all the forces on the block and add them up. That's what I was trying to guide you to. Likewise, if the system is the man, then one has to consider the works done by all the forces on the man and add them up.
Work on box by the man: 20 (100) (1) = 2000 ft x lbs
Yes.
So work done by just the man on the box is 2000 and since the work done total is zero, work done by the system would have to be -2000 lbs?
Yes, if you you rephrase it as the work done on the man.
Thank you so much for your help earlier but I needed someone present to talk it through to because this is such a weak subject for me to grasp,
I hope you have better understanding of the subject now. Face to face tutoring can be very productive.

AbbeyC172

Work done on a system is done by forces external to the system. The system cannot do work on itself. In this case if the system is block, then one has to consider the works done by all the forces on the block and add them up. That's what I was trying to guide you to. Likewise, if the system is the man, then one has to consider the works done by all the forces on the man and add them up.

Yes.

Yes, if you you rephrase it as the work done on the man.

I hope you have better understanding of the subject now. Face to face tutoring can be very productive.

Thank you for all the help! I will let you know what my professor says when he grades the paper.

"Calculate the work required to move the block"

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