91影视

A tall Styrofoam cup is filled with water. Two holes are punched in the cup near the bottom, and water begins rushing out. If the cup is dropped so it falls freely, will the water continue to flow from the holes? Explain.

(II) The gauge pressure in each of the four tires of an automobile is 240 kPa. If each tire has a 鈥渇ootprint鈥� of 190cm² (area touching the ground), estimate the mass of the car.

(II) (a) Determine the total force and the absolute pressure on the bottom of a swimming pool 28.0 m by 8.5 m whose uniform depth is 1.8 m. (b) What will be the pressure against the side of the pool near the bottom?

Two ships moving in parallel paths close to one another risk colliding. Why?

(II) A house at the bottom of a hill is fed by a full tank of water 6.0 m deep and connected to the house by a pipe that is 75 m long at an angle of 61掳 from the horizontal (Fig. 10鈥�49). (a) Determine the water gauge pressure at the house. (b) How high could the water shoot if it came vertically out of a broken pipe in front of the house?

If you dangle two pieces of paper vertically, a few inches apart (Fig. 10鈥�44), and blow between them, how do you think the papers will move? Try it and see. Explain.

Water and then oil (which don鈥檛 mix) are poured into a U-shaped tube, open at both ends. They come to equilibrium as shown in Fig. 10鈥�50. What is the density of the oil? [Hint: Pressures at points a and b are equal. Why?]

Why does the canvas top of a convertible bulge out when the car is traveling at high speed? [Hint: The windshield deflects air upward, pushing streamlines closer together.]

Roofs of houses are sometimes 鈥渂lown鈥� off (or are they pushed off?) during a tornado or hurricane. Explain using Bernoulli鈥檚 principle.

You hold a piece of wood in one hand and a piece of iron in the other. Both pieces have the same volume, and you hold them fully under water at the same depth. At the moment you let go of them, which one experiences the greater buoyancy force?

(a) The piece of wood.

(b) The piece of iron.

(c) They experience the same buoyancy force.

(d) More information is needed.