# physics (geometry bit)

posted by on .

Thanks for the help guys!!!
I really appreciate it!!!

ok I drew the thing as caerfully as I good

h t t p : / / i m g 3 7 . i m a g e s h a c k . u s / i m g 3 7 / 7 8 0 7 / f i r s t d w s . j p g

ok I redrew it chekc it

Ok I followed the directions and made a line through the point of the force of gravity parallel to the slope of the ramp...

walla I noticed a theta that I thought the triangle was and thought it was equal to the angle the ramp makes with the surface it sits on as it would appear to be but I don't know how to prove it...

ok the problem with this triangle is...

well the hypotenuse is the force of gravity which it is suppose to be

but the opposite side is y component of the force of gravity is the opposite of this triangle when it's suppose to be the adjacent...

sigh I still don't see the other triangle were the hypotenuse is the force of gravity with the opposite is the is the x component of the force of gravity

THANKS!!!

• physics (geometry bit) - ,

You still don't have it exactly. The angle equal to theta(ramp) is the other angle in the triangle in bold, at the top.

http://www.angelfire.com/stars/dhsphysics/friction.jpg

How to prove this? Similar triangles. Notice the upper angle in that photo is a right angle (ramp to Fn), in which the angle of Fn to the vertical is an angle complement to Fp and the vertical. Well, the ramp angle is also a complement to that angle. Therefore, ramp angle = angle Fn to vertical.

• physics (geometry bit) - ,

• physics (geometry bit) - ,

• physics (geometry bit) - ,

It goes there for me.

• physics (geometry bit) - ,

not for me =[

look...

h t t p : / /i m g1 3 2 . i ma g e s h a c k. u s / i m g1 3 2 / 9 1 3 7 /c a p tu r e t q i. j p g

could you try image shack upload (link below) I don't know why it wouldn't let me see it i captured the screen when i clicked on the link it's the link above

h t t p : / / i m a g e s h a c k . u s /

=]

• physics (geometry bit) - ,

h t t p : / / ww w . a n g e l f i r e . l yc o s . c o m / d o c / im ag e s / r l o a d b l oc k . j p g

• physics (geometry bit) - ,

ha ha i copied the lnik instead of clicking on it i got it thanks

• physics (geometry bit) - ,

what's fw and Fp

• physics (geometry bit) - ,

ohh ok um

Fw is the gravity

and Fp is the x component

and

Fn is the y component???

how come the x component is drawn in a weired location

but we got the triangle now thanks!!!

• physics (geometry bit) - ,

How to prove this? Similar triangles.

Notice the upper angle in that photo is a right angle (ramp to Fn),

yes and i agree right anlge

in which the angle of Fn to the vertical is an angle complement to Fp and the vertical.

angle Fn Fw

is complement to angle
fp and fw

because triangle adds up to 180 degrees ok understand

Well, the ramp angle is also a complement to that angle.

huh so angle of the ramp is complemtary to angle Fw Fp...

ok i can visually see that but how do we now these two angles are complementary???

Therefore, ramp angle = angle Fn to vertical.

I agree... now snese both angles are completary to this other angle then they must be equal

THANKS!!!