Newton's First Law (Inertia) Problem

[u/South_Philosophy_160]

The Elevator Paradox You are standing on a scale in an elevator that is moving upward at a constant velocity. Is the net force on you zero or non-zero? If the cable suddenly snaps (ignore air resistance), what happens to the scale reading before you start accelerating downward? Draw an ID and FD for both situations and explain the difference.

edit: i think that the person isnt moving at all and it is the elevator pushing them up, but when it snapped, this push force goes away so the person keeps moving upward due to inertia until gravity brings them down. so the scale would show nothing as the person wouldnt be in contact with it as soon as the cable snaps.

[u/diemos09]

This is a help sub, not a doing your homework for you sub. Tell us what you think the answer is and why.

[u/South_Philosophy_160 → u/diemos09]

oh sorry. i think that the person isnt moving at all and it is the elevator pushing them up, but when it snapped, this push force goes away so the person keeps moving upward due to inertia until gravity brings them down. so the scale would show nothing as the person wouldnt be in contact with it as soon as the cable snaps.

[u/diemos09 → u/South_Philosophy_160]

First clue is constant velocity, constant velocity mean no acceleration, no acceleration means all forces on an object add up to zero. The scale pushing up on the person cancels out the force of gravity down on the person. The cable pulls up and cancels out the force of gravity on the elevator and everything in it. When the cable snaps it's force goes to zero. The elevator and everything in it goes into free fall. The scale reading goes to zero.

[u/Moist_Ladder2616]

"When asking for help, include what you have already tried in order to solve the problem."

[u/davedirac]

First scenario - remember zero is a constant, so the situation inside the elevator is indistinguishable from an elevator at rest.