Search
Ask a question
0

Find the scale reading?

A person with mass of 55 kg is standing on a scale in an elevator. The elevator is moving up and accelerating at 1.5 m/s^2 for 3 seconds, then continues with constant speed. Find the scale reading a) before starting to move, b) when accelerating, c) when moving at constant speed?

1 Answer by Expert Tutors

Tutors, sign in to answer this question.
Alex V. | College doesn't make you smart. College teaches you to be resourceful.College doesn't make you smart. College ...
4.8 4.8 (73 lesson ratings) (73)
1
Check Marked as Best Answer
Sum of the forces in the vertical direction Fy = F+ (-mg) = ma
 
(a) At rest, ma= 0.
Scale reading is equal to FN and is equal to (mg)
FN = 55kg *(9.8m/s) = 539 N = 121 lbs
 
(b) at a=1.5m/s2
FN = mg + ma = (55kg)(9.8m/s2) + (55kg)(1.5m/s2) = 621.5 N = 140 lbs
 
(c) at constant speed, a = 0,
same as (a) scale reading is equal to FN = 539 N = 121 lbs