A 62 kg student stands on a scale in a lift.
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
A student stands on a scale in a lift. What does it read when the lift
- goes up at a steady speed;
- speeds up upward at ;
- speeds up downward at ;
- falls freely? (.)
Need a reminder? The key ideaShow
A scale shows the push it gives, with up positive. In free fall, including in orbit, and the scale reads zero: that is weightlessness, not an absence of gravity.
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. (a) : .
Step 2. (b) .
Step 3. (c) .
Step 4. (d) : .
Answer: (a) . (b) . (c) . (d) .
Watch out. A steady speed, up or down, gives the true weight; only acceleration changes the reading.
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