What does this scale read?

Question

Ronald Ripvance has a mass of 50kg. Ronald stands on the scale in an elevator traveling upward at a constant speed of 2.5 m/s.

A. What does the scale below Ronald read? (in newton’s)

B. The elevator then slows to a stop at a rate of -5 m/s squared. What does the scale read as the elevator slows to a stop?

C. The elevators steel cables suddenly break and the elevator falls toward the ground in free fall. What does the scale below Ronalds feet read now?

Thank you! Have a wonderful night.

Answer 1

A) At constant speed, acceleration a = 0 and normal force F_N of the scale on Ronald is just his weight mg = 50*(9.8) = 490 N (500N if using g = 10).

B) Now a = -5, the sum of vertical forces ΣF_y = F_N - mg = ma, so F_N = 490 + 50*(-5) = 240 N (250N for g = 10).

C) F_N = 0, "weightless" because Ronald is falling at the same rate as the scale, just as astronauts in the ISS are all falling around Earth at the same rate.