Physics (10th Edition)

Published by Wiley
ISBN 10: 1118486897
ISBN 13: 978-1-11848-689-4

Chapter 4 - Forces and Newton's Laws of Motion - Problems - Page 118: 97

Answer

(a) The apparent weight is $1102N$ (b) The apparent weight is $931N$ (c) The apparent weight is $807.5N$

Work Step by Step

(a) As the person stands in the elevator moving upward with $a=1.8m/s^2$, she is under the influence of her weight $mg$, which points downward, and the normal force $F_N$, which points upward. $$F_N-mg=ma$$ Here, the number registered in the scale is the value of $F_N$, which is her apparent weight. $$F_N=m(g+a)=95(9.8+1.8)=1102N$$ (b) The elevator moves upward at $a=0$, meaning $$F_N-mg=0$$ $$F_N=95\times9.8=931N$$ (c) The elevator moving downward only changes the sign of $a$ $(a=-1.3m/s^2)$; the person is still under these same two forces: $$F_N-mg=-ma$$ $$F_N=m(g-a)=95(9.8-1.3)=807.5N$$
Update this answer!

You can help us out by revising, improving and updating this answer.

Update this answer

After you claim an answer you’ll have 24 hours to send in a draft. An editor will review the submission and either publish your submission or provide feedback.