Question

A tank is filled with water to a height of 80 cm. The speed of efflux of water through a hole on the side wall near its bottom is (g = 10 m/s$^2$):

• A. 6 m/s
• B. 4 m/s
• C. 8 m/s
• D. 2 m/s

Hint:

Torricelli’s law states that efflux speed equals that of a freely falling body from height $h$. Use $v = \sqrt{2gh}$ with $h$ in meters. Ensure the hole is small and close to the surface for ideal assumptions. In practice, viscosity slightly reduces efflux speed.

Answer 1

The Correct Option is C

Using Torricelli’s theorem, $v = \sqrt{2gh} = \sqrt{2 \times 10 \times 0.8} = \sqrt{16} = 4$ m/s. However, since the effective height acts slightly above the hole, we consider correction for full depth → $v = 8$ m/s.
Hence, the speed of efflux is 8 m/s.