- #1
daveyman
- 88
- 0
This question was presented as one of those "think about it" questions in my physics class. Its not worth any points, but its driving me crazy! I can't figure it out. Here it is:
Consider a pineapple sitting on a sensitive scale resting
on the bottom of a large glass jar which is connected to a
vacuum pump. The reading on the scale is 2.315 pounds
with air in the jar. The air is now pumped out of the
jar. Which of the following gives the best description of
what happens to the scale reading and why.
(a) The scale reading increases slightly because the
buoyant force of the air is now gone.
(b) The scale reading decreases slightly because the
air used to be pushing down on the pineapple, but now
it isn’t anymore.
(c) Weight is caused by gravity and doesn’t have anything
to do with the air, so the reading stays the same.
(d) The reading decreases slightly because the scale
reading used to include the weight of the air in the jar,
but now the air is gone.
Consider a pineapple sitting on a sensitive scale resting
on the bottom of a large glass jar which is connected to a
vacuum pump. The reading on the scale is 2.315 pounds
with air in the jar. The air is now pumped out of the
jar. Which of the following gives the best description of
what happens to the scale reading and why.
(a) The scale reading increases slightly because the
buoyant force of the air is now gone.
(b) The scale reading decreases slightly because the
air used to be pushing down on the pineapple, but now
it isn’t anymore.
(c) Weight is caused by gravity and doesn’t have anything
to do with the air, so the reading stays the same.
(d) The reading decreases slightly because the scale
reading used to include the weight of the air in the jar,
but now the air is gone.