Weight in an elevator? Free body diagrams

A 60kg student is standing on a scale in an elevator that measures weight in newtons. Calculate the reading on the scale if the elevator is accelerating down at 4 m/s^2…..when the elevator is accelerating up at 4 m/s^2…. and in free fall.

Not sure if my work/answer is correct

accelerating down (up is positive)
Fnet= Fn – Fg
ma = Fn – mg
(60)(-4)= Fn – (60)(-9.8)
-240 = Fn +588
Fn = -828
∴ Fn = 828 N(Down)

accelerating up (up is positive)
Fnet = Fn – Fg
240 = Fn +588
Fn = -348
∴Fn = 348 N(down)

Free fall: the weight of the student is the same as if he/she were standing on the ground(588N) since gravity is still present and the student’s mass remains constant.

http://ift.tt/OTtUob

Leave a comment

Your email address will not be published.


*


Show Buttons
Hide Buttons