state gov RPSC 2nd Grade Senior Teacher Mock Test Series 2025 Physics Thermal Properties of Matter Newton’s law of cooling
A solid copper sphere (density \( \rho \) and specific capacity C) of radius r at an initial temperature of 200 K is suspended inside a chamber whose walls are at almost 0 K. The time required for the temperature of the sphere to drop to 100 K is
1
\( \displaystyle \frac{7r\rho C}{72 \times 10^6 \sigma} \)
2
\( \displaystyle \frac{r \rho C}{6\sigma} \)
3
\( \displaystyle \frac{r \rho C}{\sigma} \)
4
none of the above.
5
Question Not Attempted