Pressure+Problems

4. A section of granite floor is capable of sustaining 500 P.A. of pressure. If a 2000kg rectangular weight of dimensions 10m X 4m is resting on it, will the granite floor break? (Hint, use F=MA, then P=F/A)

7. For obvious reasons, men on stilts are not allowed in rooms with styrofoam floors. If Styrofoam floors collapse under pressures above 24,000 ppi and a stilt man accidentally wanders in wearing stilts with a radius of .05 meters and weighing 50 kg, would he Styrofoam floor be pierced? (Area of a Circle=2 pi r^2)

11. Somehow, a glitch in time occurs and your car is transplanted onto a possum. If your car is 4000 kg, a possum is crushed at 15,000 ppi, and at any given time only .4 sqr. meters of each tire is touching the ground, will the possum get crushed under one of your tires?

12. Imagine that you find a pin so small that it is virtually invisible. If the tip of the pin is only .000001 sqr. meters, how hard would you have to push to penetrate a metal from mars that resist a pressure of 500,000,000 ppi? Is this possible for a mere mortal?

17. Your super-light travel umbrella has a mass of 200 g. If you are balancing its tip, approx. 3 cm2, on your finger, what pressure is being put on your finger? What if it’s raining, and the rain on the umbrella adds a force of 2 N? (F=MA, for the weight of the umbrella, then P=F/A)

4. ma=f (2000kg)(-9.8)=F F=-19,600 N P=F/A =19,600 N / 40m2 =490 P.A. 500 P.A. > 490 P.A. No, the floor will not break.

7. A = (3.14)(r^2)(2) A = .0157 m^2 P = F/A P = (50)(9.8)/(.0157) = 31,210 There goes the floor.

11. P = F/A P = (4000)(9.8)/(.4)(4) P = 24,500 24,500 > 15,000 so the possum is crushed!!

12. P = F/A P = (F)/(.000001) = 500,000,000 F = 500 ppi It’s easy

17. The Answer will be posted later.