Question

The diameter of the tap of a fire brigade pump is $5cm$. Water is thrown by this pump at a horizontal speed of $18m/s$ on a wall. If water rebounds back with same velocity from the wall, then the force exerted by water on the wall will be:

• A. $2.35\times {10}^{5}dyne$
• B. $5.76\times {10}^{6}dyne$
• C. $6.36\times {10}^{7}dyne$
• D. $12.72\times {10}^{7}dyne$

Answer 1

Answer: (D)

$12.72\times {10}^{7}dyne$

From the concept,
$F=2dA{v}^2$
$d=1g/{cm}^3$
$A=\frac{\pi }{4}\times 5^2{cm}^2$
$v=1800cm/s$
So, $F=12.72\times {10}^{7}dyne$