Question

A stone of mass $5 \,kg$ is tied to a string of length $10 \,m$ and is whirled round in a horizontal circle. What is the maximum speed with which the stone can be whirled around if the string can withstand a maximum tension of $200 \,N$?

• A. $10\, m$ $s^{-1}$
• B. $15\, m$ $s^{-1}$
• C. $20\, m$ $s^{-1}$
• D. $25\, m$ $s^{-1}$

Answer 1

Answer: (C)

$20\, m$ $s^{-1}$

Answer 2

Here, $m=5\, kg$ , $r=10 \,m$, $T_{max}$ $=200\,N$ As $T_{max}$ $=\frac{mv^{2}_{max}}{r}$ $\therefore$ $v^{2}_{max}$ $=\frac{T_{max}\times r}{m}$ $\therefore$ $v^{2}_{max}$ $=\frac{200\times10}{5}=400$ $\quad\Rightarrow$ $v_{max}$ $=20 \,m$ $s^{-1}$