Question 302: Properties of Matter

Question

A thin flat circular disc of radius $$4.5 \mathrm{~cm}$$ is placed gently over the surface of water. If surface tension of water is $$0.07 \mathrm{~N} \mathrm{~m}^{-1}$$, then the excess force required to take it away from the surface is

Accepted Answer

$$
\begin{aligned}
& 	ext { Excess force }=T 	imes 2 \pi R \
& =\frac{7}{100} 	imes 2 	imes 3.14 	imes \frac{4.5}{100} \
& =197.82 	imes 10^{-4} \
& =19.8 	imes 10^{-3} \mathrm{~N} \
& =19.8 \mathrm{~mN}
\end{aligned}
$$

Answer

19.8 mN

Answer

198 N

Answer

1.98 mN

Answer

99 N

Properties of Matter

A thin flat circular disc of radius $4.5 \mathrm{~cm} is placed gently over the surface of water. If surface tension of water is 0.07 \mathrm{~N} \mathrm{~m}^{-1}$, then the excess force required to take it away from the surface is

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