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equilibruim and motion problem
- Thread starter badkins
- Start date
Manuel weighs 1000N, and stands in the middle of a board that weighs 200N. The ends of the boards rest on bathroom scales. Board acts at its center. Fill in the correct weight reading on each scale/
The given problem is straight forward and intuitive. Both Manuel and the center of the board are equidistant from the two scales. Their weight will be equally carried/supported by the two scales. Add their weights and divide by 2:
(1000N + 200N)/2 = 600N on each scale.
For a more general solution, consider this example: Let two scales, A and B, be 10 meters apart, and there are two weights on the weightless board between them.
One weight is 5N and is 2 meters from A (and 8 meters from B).
The second weight is 8N and 4 meters from A (and 6 meters from B).
To find the reading/reaction at B, we calculate the moment at A (by multiplying the weight times the distance from A:
(5N)(2m) = 10 N-m
(8N)(4m) = 32N-m
Total moment about A is 10 + 32 = 42 N-m.
The reaction at B has to counter this moment. Therefore, to calculate the scale reading at B, just divide the moment at A by the distance of B from A (10m):
42N-m/10m = 4.2 N
We could do a similar calculation of moments about B to find the scale reading at A, but there is an easier way. The sum of the scale readings must equal the applied weights (5N and 8N). Therefore the reaction (scale reading) at A is simply:
(5N + 8N) – 4.2N = 8.8N
Hope that helps.
Hi
Thank-you for your response. the answer my book gives is (a) 30N + 20N= 50N
(b) 30N-20N= 10N
It state the equilibrium rule EF= 0 now I not sure how to solve for this problem could someone shed more light on this problem
All help is really appreciated
Thank-you for your response. the answer my book gives is (a) 30N + 20N= 50N
(b) 30N-20N= 10N
It state the equilibrium rule EF= 0 now I not sure how to solve for this problem could someone shed more light on this problem
All help is really appreciated
D
Deleted member 4993
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Manuel weighs 1000N, and stands in the middle of a board that weighs 200N. The ends of the boards rest on bathroom scales. Board acts at is center. Fill in the correct weigh reading on each scale/
badkins said:Hi
Thank-you for your response. the answer my book gives is (a) 30N + 20N= 50N
(b) 30N-20N= 10N
It state the equilibrium rule EF= 0 now I not sure how to solve for this problem could someone shed more light on this problem
All help is really appreciated
I am almost sure - you are looking at the answer for wrong problem. In your stated problem there is only one "situation"
Yet
The answer you post has (a) and (b) - how is that??
Of course the numbers (posted as answers) don't make sense (referring to the original) either!!