# Homework Help: Force normal to plate

1. Apr 6, 2016

### foo9008

1. The problem statement, all variables and given/known data
the figure showed a jet of water , with velocity 50m/s strikes the flat plate , which is inclined 30 degree to the jet . Find the force normal to the surface of jet.

2. Relevant equations

3. The attempt at a solution
my question is the flat plate is 30 degree to the horizontal axis ? or vertical axis ? i'm consfuing

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2. Apr 6, 2016

### haruspex

It doesn't matter. It is only asking about the force resulting from the deflection of the stream of water. Which way gravity acts is of no consequence.

3. Apr 6, 2016

### foo9008

My ans would be different, the formula given is rho(A)(v^2)cos theta , where theta is the velocity normal to the plate , if the angle 30 is from horizontal axis, then my theta would be 60, am I right??

4. Apr 6, 2016

Here

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5. Apr 6, 2016

### haruspex

Oh, you only meant vertical and horizontal with respect to the way you drew the diagram.
So what you are really asking is what does it mean to say the plate is at 30 degrees to the jet. I agree it's not crystal clear, but I would take it to mean that the normal to the plate is at 60 degrees to the path of the jet.

6. Apr 6, 2016

### foo9008

So my idea that theta=60 is correct?

7. Apr 6, 2016

### haruspex

As in your second attachment, yes.