An open large tank of cross section area $1000{ \mathrm{cm}}^2$ and height $5 \mathrm{m}$ is completely filled. There is a small hole near the bottom of tank of area $1{ \mathrm{cm}}^2$. Then time taken to $\left(g=10 {\mathrm{ms}}^{-2}\right)$

Two cubical blocks of same dimensions but masses $m$ and $3 m$ are joined by a string and are at equilibrium in water as shown in figure. Then

A liquid is rotated in a cylindrical vessel about its axis with constant angular speed, then

A soap film is made on a $U$-shaped frame with a sliding bar as shown. The frame is in vertical plane. If surface tension of soap solution is $0.3 {\mathrm{Nm}}^{-1}$, then find the mass of slider in grams $\left(g=10 {\mathrm{ms}}^{-2}\right)$