Warm-Up Exercise 1 - Answers

Due 12:15 pm, Mon 27 Aug 2012

Physics 123, Fall 2012

Imagine taking a thumbtack between your thumb and forefinger, with the sharp end on your thumb and the tail end against your forefinger (even though each end of the tack exerts the same pressure). If you squeeze, it's immediately painful on your thumb but not your finger. Why? (Don't refer back to the text.)

Each end of the tack exerts the same *force*, but the sharp end exerts that force over a smaller area (hence, bigger *pressure*; P=F/A).

Is it possible for two fluids to exert a different pressure on a submerged object? Explain why or why not?

Yes, if their densities are different, they will exert different pressures on any object submerged in them. (The denser one will exert the greater pressure at the same depth.)

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