Forces in a dynamic problem

  • #1
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Homework Statement



A 40kg person is falling at the speed of gravity, 9.8m/s^2. Wind resistance is not considered. On your free-body diagram, the direction they are falling (ground) is in the negative direction, hence gravity is causing an acceleration in the negative.

Homework Equations



F(gravity) = (40)(-9.8)
F(gravity) = -392N

The Attempt at a Solution



I am simply curious when solving a problem such as this, would N be a -392N since it is traveling in the negative on the free-body diagram, or is it seen a magnitude and considered a positive number?
 

Answers and Replies

  • #2
461
8
I am simply curious when solving a problem such as this, would N be a -392N since it is traveling in the negative on the free-body diagram, or is it seen a magnitude and considered a positive number?
Force is a vector therefore it has a direction. Also the direction of the movement of the object and the direction of the force do not have to me the same. For example a ball going up after you throw it moves up but the force acting on it is downward.
 
  • #3
328
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Thank you.
 

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