Random act of science teaching - you weigh less on the way down in the an elevator
June 7th, 2008 Posted in Physics Talk
Random act of science teaching. These scales were mounted inside commercial and residential elevators allowing riders to test this fact.
Explanation was available as a leaflet in the the elevator.
Everyday physics, tested by everyday person, using everyday objects.
June 8th, 2008 at 4:29 pm
Now instead of dropping overweight Americans will live in elevators.
June 9th, 2008 at 6:19 pm
Oh, sure, I weigh less as we start down, but I gain it all back as we travel, and I weigh even more as we stop on the first floor.
Dang crash diets!
November 18th, 2008 at 9:27 am
Surely you weigh less only while the elevator is _accelerating_ downward?
November 30th, 2008 at 4:54 pm
Um…that scale is completely misleading. You do not weigh any different whether you are moving up, down, left, right, or even accelerating up, down, left or any which way.
Weight is another name for the force of gravity, and that can only be changed if you change your mass or move to a different planet - both of which do NOT change while in an elevator.
The scale is actually measuring the force that you exert on it, otherwise known as a normal force (because it is perpendicular to the surface). Typically the normal force that the scale exerts on you is equal to your weight because there is no acceleration. When forces balance, there is no change in your motion.
However, when you accelerate upward or downward in an elevator, you need the normal force and your weight to NOT be balanced, so therefore the scale can read something different.
If you are simply traveling downward without any acceleration, the forces are balanced and the normal force that the scale exerts on you is equal to the force that the Earth exerts on you….so you do NOT weigh less when moving downward in an elevator.
Your apparent weight (the normal force caused by the scale on you) will register less when you are accelerating down.
Sheesh! Take a physics class before you advertise how good you are at physics.
December 1st, 2008 at 2:08 am
Actually, “weight” is a measure of how much normal force you exert on whatever the “ground” is, in this case the elevator. So yes, you weigh less when moving down the elevator.
Sheeesh! Try general relativity before spouting of about elevators.
December 1st, 2008 at 3:40 am
“Weight is another name for the force of gravity, and that can only be changed if you change your mass or move to a different planet - both of which do NOT change while in an elevator.”
Gravity is not a force, gravity is an acceleration. The elevator changes the acceleration, so it also changes the gravity.
Also, gravity does change with elevation, so people farther away from sea level will weigh move.
December 1st, 2008 at 10:22 pm
Gravity is a force. One of the elemental forces, if you want to put it that way. Force makes you accelerate -> acceleration = force
December 2nd, 2008 at 3:23 pm
The force will be with you…..always..
December 2nd, 2008 at 4:08 pm
force = mass*acceleration
technically you gain “weight” but your mass stays the same, as stated above the normal force it a measure of the normal force you exert upon an object.
gravitational acceleration comes into play with 9.82 m/s²
total acceleration = gravitational acceleration + lift acceleration
when the lift rises the acceleration used to increase the speed of the lift (moving up and down) initially acts with the 9.82 m/s² from the force due to gravity to increase the over all force, when the lift approaches the correct floor the lift then slows giving it negative acceleration which acts against the force due to gravity.