Question Detail

PHY 101 Surface Tension Objective Question
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Question

In an example calculation for sap rising in a tree, the required radius of a capillary tube to raise sap 100 m was found to be approximately 1.41 × 10⁻⁷ m. The actual xylem tubes in trees have radii as small as 2.5 × 10⁻⁵ m. What does this comparison suggest?
Options
A Capillary action is more than sufficient to explain sap rise.
B Capillary action alone cannot be solely responsible for sap rising to the tops of tall trees.
Correct Answer
C The calculation must have used the wrong surface tension value.
D Tree sap has a much lower density than assumed.
Correct Answer

Option B is the correct answer.

Detailed Explanation

The calculated radius required for capillary action alone to raise sap 100 m is about 180 times smaller than the actual radius of xylem tubes. Since the capillary rise is inversely proportional to radius, the rise in actual tubes would be much less than 100 m. This indicates that capillary action is not the primary mechanism and other factors are involved.

Hint

Compare the calculated radius with the actual radius. How does the capillary rise height change with radius?

Question Info

Course: PHY 101
Topic: Surface Tension
Type: Objective
Difficulty: Not specified
Question 729 of 1250
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