Answer, and give a reason. At 550 km up, where a space telescope orbits, is g zero?
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
Answer, and give a reason.
- At up, where a space telescope orbits, is zero? Estimate it. (, .)
- Why do the astronauts there feel weightless?
- Could they weigh themselves on a bathroom scale?
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) No: , about of the surface value.
Step 2. (b) They and their craft fall around the Earth together with that acceleration, so nothing pushes on them.
Step 3. (c) No; the scale would fall with them and read zero. Astronauts measure their mass with a spring that sets them oscillating: the period gives the mass.
Answer: (a) . (b) Free fall. (c) No, but a vibrating spring can measure mass.
Watch out. Weightless is not the same as massless: they still need force to start and stop.
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