A 100 kg person stands on a scale. a.) What would be the scale readout? N (How d

Question

A 100 kg person stands on a scale.

a.) What would be the scale readout?


N
(How does this compare with the person's weight?)

Now, find a general expression for the scale readout, in terms of the person's mass, acceleration, and/or g.
Show that it can be used to get the answer for part a above, and then use it to get the answers for all of the following parts:

b.) If the person stands on the scale in an elevator accelerating upwards at 7 m/s2, what is the scale readout?


N
(How does this compare with the person's weight?)

c.) If the person stands on the scale in an elevator accelerating downwards at 7 m/s2, what is the scale readout?


N
(How does this compare with the person's weight?)

d.) If the person stands on the scale in an elevator accelerating downwards at 9.8 m/s2, what is the scale readout?


N
(How does this compare with the person's weight?)

e.) Explain why your result from part d makes sense. Is the actual weight of the person any different? What does the person perceive his weight to be?



f.) If the person stands on the scale in an elevator moving up at a constant speed of 100 m/s, what is the scale readout?
N
(How does this compare with the person's weight?)

Explanation / Answer

a 100kg person stands on a scale? a.) What would be the scale readout? ___ N (How does this compare with the person's weight?) w = W - C = mg - mw^2r; where m = 100 kg, g = 9.81 m/sec^2, w = 2pi rad/24 hours [you need to change this to rad/sec], and r = R cos(L) Earth's radius of rotation at a given latitude L and the radius of Earth R. w is the net weight you are looking for, it's what you will read on the scale. In most daily problems, we can ignore centrifugal force C and set it to C = 0. If C = 0, the w = W = mg, which is the weight in Newtons. b.) If the person stands on the scale in an elevator accelerating upwards at 5 m/s2, what is the scale readout? ____N (How does this compare with the person's weight?) w = W + ma = mg + ma = m(g + a); where a = 5 m/sec^2. Is the net weight w greater or lesser than W? c.) If the person stands on the scale in an elevator accelerating downwards at 5 m/s2, what is the scale readout? ___N (How does this compare with the person's weight?) w = W - ma = m(g - a); again is w > W or ,

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