Teaching Physics with the Physics Suite

Edward F. Redish

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Go with the flow

For each of the items below complete the sentence with quantitative words. Use words such as “not change”, “double”, “triple”, “halve”, etc. If you prefer, you may write, =, X2, X4, ÷2, ÷3, to mean equal, doubled, quadruples, halved, divided by three, etc. (Note that “increases” or “decreases” is NOT sufficient.)

(a) The interior of a water pipe bringing water into your hot water heater has narrowed as a result of the buildup of scale from the fact that your water is very hard (contains dissolved chemicals). The radius of the open area inside the pipe has decreased by a factor of two. If the pressure differential remains the same, the flow into the heater will _______.

(b) You have a single window in the wall of your kitchen and you are contemplating putting a second identical window into that wall. In the winter, for a given inside-outside temperature difference, that change will ________ the flow of heat out of your house through the windows in that wall.

(c) Blood is flowing through an artery that has a partial blockage in a part of the artery so that half its cross sectional area is blocked. In the part with the blockage, the velocity of the blood is ________ the velocity of the blood in the unblocked part of the artery.

(d) I blow as hard as I can through a single straw. If instead, I blow as hard as I can through two straws (of the same length as the single straw) placed side by side, the rate of flow will ________.

Page last modified December 11, 2010: M30