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 Jul 16th 2018, 05:32 AM #1 Junior Member   Join Date: Jul 2018 Posts: 5 check my answer A man ran up the road. Air resistance is negligible. We have before us a proposal to draw up forces. The forces that operate on the man according to the chart are: mg weight; N strength of the clamp; * f friction force; * D power of the man. How many errors are there in the proposal? Choose one answer: 0 1 2 3 More than 3 I think there is only one error of weight. What do you think ?
 Jul 16th 2018, 06:11 AM #2 Senior Member     Join Date: Jun 2016 Location: England Posts: 1,000 This is a more subtle question than it first appears, and requires some careful thought. There are two "primary" forces shown, and two "reaction" forces. __________________ ~\o/~
Jul 16th 2018, 06:14 AM   #3
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 Originally Posted by Woody This is a more subtle question than it first appears, and requires some careful thought. There are two "primary" forces shown, and two "reaction" forces.

 Jul 16th 2018, 07:28 AM #4 Senior Member     Join Date: Jun 2016 Location: England Posts: 1,000 Errors imply measurements. The upward force must equal the downward force, to stop the man either flying or falling through the floor. Similarly the friction force must equal the pushing force, (unless he is slipping at each step). The mass of the man will have to be measured, as will the power with which he is pushing his body forward. __________________ ~\o/~
Jul 16th 2018, 09:59 AM   #5
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 I think there is only one error of weight. What do you think ?
I think you are just guessing.

Work through each of the proposed forces systematically and state whether you think they are correctly displayed or not and state why.

Hint: one is correct; three are incorrect.

Last edited by studiot; Jul 16th 2018 at 12:40 PM.