Question

18. A stream of water of density d, cross-section A and speed v strikes a wall that

is perpendicular to the stream as shown. The water then flows sideways along the wall. The force exerted by the stream on the wall is -

Answer 1

Answer:

dAvsquare /2

Explanation:

refer the figure

Answer 2

The force exerted by the stream on the wall is $du^2A$.

Step-by-step Solution:

Given:

• The density of stream of water = d
• Area of cross section= A
• Speed of stream of water = v
• Wall is perpendicular to the stream.

To be found: The force exerted by the stream on the wall.

Formula used: $F=\frac{dp}{dt}$

Solution:

Since we know that stream of water strikes a wall that is perpendicular to the stream, we can visualize this by the following diagram attached below:

Now using the formula,

$F=\frac{dp}{dt}$

where $p=mu$

Now, our equation will be,

$F=\frac{d(mu)}{dt}$
Now we know,

$\frac{dm}{dt}= density\times area \times speed\\ \frac{dm}{dt}=d\times A\times u$

Now, putting in the equation,

$F=\frac{dm}{dt}\times u\\F=d\times A\times u \times u\\ \therefore F=du^2A$

So, the force exerted by the stream on the wall is $du^2A$.