Download Apparent Weight

Apparent Weight
Apparent Weight
• https://www.youtube.com/watch?v=7wVmXRd764
Advanced Application of the 2nd Law
• A gentleman in brown shoes stands on a scale
that measures forces in pounds. The scale reads
202lbs. The man brings the scale into an elevator.
When he is on the scale in a stationary elevator, it
reads 202lbs. After a friend has pushed a button
for a different floor, the scale reads 180lbs for a
second or two, before returning to 202lbs for
several seconds. Then, the reading changes to
216lbs for a second or two before returning to
202lbs. Describe (qualitatively) the trip the
elevator made.
How do you feel when the elevator…
•
•
•
•
•
•
•
starts an upward trip?
moves upward at a constant velocity?
slows at the end of an upward trip?
starts a downward trip?
moves down at a constant velocity?
slows at the end of a downward trip?
Why do you feel these ways? What force is
changing size?
FBD for riding an elevator:
Which force changes when the elevator accelerates?
FN
Fg
Advanced Application of the 2nd Law
• A man stands on a scale that measures forces in
pounds. The scale reads 202lbs. When he is on
the scale in a stationary elevator, it reads 202lbs.
After a friend has pushed a button for a different
floor, the scale reads 180lbs for a second or two,
before returning to 202lbs for several seconds.
Then, the reading changes to 216lbs for a second
or two before returning to 202lbs. Compute the
acceleration of the elevator for while…
– The scale reads 180lbs
– The scale reads 216lbs
Elevator “Lab”
• While stationary a spring scale measures a
force of 1.96N when a brass cylinder is
hanging on the scale. While riding in an
elevator that is starting the trip up (from the
first to the third floor) the scale reads 2.01N.
Determine the acceleration of the elevator.