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Person as a .

External influences from the earth (gravity) and the floor of the elevator (normal force).

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h2. Part B

Suppose a person with a weight of 686 N is in an elevator which is ascending at a constant rate of 1.0 m/s and slowing down at a rate of 3.0 m/s{color:black}^2^{color}.  What is the person's apparent weight?

h4. Solution

*System, Interactions and Model:* As in Part A.

*Approach:*  As in Part A, the acceleration is negative in our coordinates.  The free body diagram is also the same, and so we find the same result:

{latex}\begin{large}\[ N = \mbox{476 N} \]\end{large}{latex}

h2. Part C

Suppose a person with a weight of 686 N is in an elevator which is ascending at a constant rate of 1.0 m/s and speeding up at a rate of 3.0 m/s{color:black}^2^{color}.  What is the person's apparent weight?

h4. Solution

*System, Interactions and Model:*  As in Part A.

*Approach:*  The free body diagram and form of Newton's 2nd Law is the same as in Part A, except that the relative size of the forces will be different.  We can see this by writing Newton's 2nd Law for the y-direction:

{latex}\begin{large}\[ N = ma_{y} + mg \]\end{large}{latex}

This time, however, the acceleration is positive (_a_~y~ = + 3.0 m/s{color:black}^2^{color}) giving:

{latex}\begin{large}\[ N = \mbox{896 N} \] \end{large}{latex}

{tip}Upward acceleration increases the perceived weight.{tip}