frictional forces

[Danlee07]

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Book says that Nx = mg cos Ɵ. what am i missing??? i'm doing all this so i can find the x component of acceleration so that i use that into the displacement equation

This is the question and my reasoning:
A trained sea lion slides from rest with constant acceleration down a 3.0 m long ramp into a pool of water. If the ramp is inclined at an angle of 23 degrees above the horizontal and the coefficient of kinetic friction between the sea lion and the ramp is 0.26, how long does it take for the sea lion to make a splash in the pool?

I drew out the free-body. Ny = N. Nx = 0. When I use N in frictional forces equation, isn't it Ny? So when I use N in sum of all forces of x component N should equal 0? But in the book, it isn't 0. Can someone explain this

 

[Danlee07]

Oh i figured it out... doh

the normal force in the frictional forces equation is just N so that means it's y component not x.

actually a follow up question though:
i know that static and frictional aren't related, but why is that all the values that I see for static are > 1 and most of the frictional are <. It says "Beyond the max static friction value, sliding begins, and the friction is kinetic and has a magnitude less than the max static friction value." Is 1 like a comparison value?? So more than 1 is static and less than 1 is kinetic frictional? I don't get how they're connected.. since i thought once it starts to move, it's completely kinetic. Why is the kinetic value less than max static frictional?

 

[Fifty 3rds]

Static is always higher than kinetic. It is always harder to force something into movement than it is to continue on it's path.

No matter the surface!

I'm not sure of the values. It could be relational, but probably not, since your static is higher than 1. I don't know what the reference would be.

Any surface, even one with extreme kinetic frictional force, will have a higher static frictional force.

The only way a test question could present a frictional force higher than the static, would be if the object moved across two mediums/surfaces. Think marble/teflon and asphalt or anything extreme.

And to be honest, I haven't seen one of those questions yet.

I hope this makes sense.