## Elavating Ramp

A block is at rest on an inclined plane whose elevation can be varied. The coefficient of static friction is = 0.37, and the coefficient of kinetic friction is = 0.15. The angle of elevation is increased slowly from the horizontal.

At what value of does the block begin to slide (in degrees)?

At what value of does the block begin to slide (in degrees)?

**What is the acceleration of the block?****2.031×101**

**2.022 m/s^2**## Discussion

**help**

*Anonymous 1*(Thu Jan 21 12:26:30 am 2010 (EST))

I am doing this problem EXACTLY how we were shown in class

and i am getting the answer wrong.. can someone explain this?

i am using Theta= tan^-1 (Mu s)

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*Anonymous 2*(Thu Jan 21 03:26:32 pm 2010 (EST))

any help on part 2?

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since the static friction equals tan(theta), you have to use the inverse of tangent

to find the angle. Hope that helps.

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for part 2

newton 2 says EF=m*a

you can ignore forces on the y axis

forces on x: forward force -Friction

EF= m*g sin(theta) - muK * N

EF= m*g sin(theta) - muK * m*g*cos(theta)= m*a

solve for a

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*Anonymous 4*(Thu Jan 21 07:54:52 pm 2010 (EST))

for part 2 what is m?

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The mass isn't provided. You have to use the equation that

Dr. Ing gave us last lecture which was:

a = g(sin theta) - (mu k)*(cos theta)

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*Anonymous 4*(Fri Jan 22 01:45:19 pm 2010 (EST))

I am using the eqn 9.8(sin theta i got for part 1)- mu K

(cos theta i got for part one) and im not getting it right?

Any help? I may be putting in the wrong units?

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**Re: help**

*Anonymous 6*(Fri Jan 22 03:19:50 pm 2010 (EST))

Just make sure that your calculator is in degrees rather

than radians and it should work out.

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I'm having the same problem,

I have a=9.8(sin 19.3)-.16(cos 19.3)

So my a is 3.088 m/s^2

But it's incorrect according to Lon Capa. Anyone have a clue

where I'm messing up?

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the equation is a=g((sin theta)-(mu k)(cos theta))..make

sure g isn't just multiplied by the sin theta and the

answer should be correct

**NEW**

Thank you, that was exactly the problem!