Answer:
30 N
Explanation:
there are two forces act on the bar:
- weight of 1.5 kg mass, w = mg = 15 N
- weight of the bar, wb
for balance,
w * Lw = wb * Lwb
Lw = length of bar from the mass to the pivot
Lwb = lenght of bar from the center of the bar to the pivot
15 * 20 = wb * (50-20)
300 = wb * 30
wb = 300/30 = 30 N
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Surface tension is a property of a liquid to resist the external force. It is the result of cohesive forces between the molecules of the liquid.
The stronger the cohesive forces between the molecules of the liquid, the stronger is the surface tension.
Since methylated spirit has weaker cohesive forces than water, it will also have a weaker surface tension.
Hey! I know you've probably already finished the quiz already, but I just wanted to let you know the correct answer should be D. I wish I could tell you why, but I ended up getting that answer through a bit of trial and error myself... Anyway, good luck!
