Jump to content
Sign in to follow this  
Radagast

Inclined Ramp/Friction Problem:

Recommended Posts

In the diagram, a person is pushing down on top of block 2 to hold blocks 1 and 2 at rest. Block 1 has a mass of 10kg and block 2 has a mass of 8kg. The coefficent of static friction between 1 and the ramp is 0.25 . When a person removes his hand...

 

a) Will block 1 slide down the ramp?

 

b) What is the minimum coefficent of static friction between block 1 and block 2 such that block 2 will not slide on block 1?

 

I'm having problems understanding this question, particularly part B. Any hints to send me in the right direction or explanations on the proper method to solve would be appreciated. My textbook doesn't seem to have an example quite like this one.

physq.jpg

Share this post


Link to post
Share on other sites
Start by drawing a free-body diagram.

 

Ding ding ding.

Share this post


Link to post
Share on other sites

That is the worst question I've ever seen. lol you state that "a person is pushing down on top of block 2 to hold blocks 1 and 2 at rest." and then you ask "a) Will block 1 slide down the ramp?" ..........

Share this post


Link to post
Share on other sites
That is the worst question I've ever seen. lol you state that "a person is pushing down on top of block 2 to hold blocks 1 and 2 at rest." and then you ask "a) Will block 1 slide down the ramp?" ..........

 

When a person removes his hand...[/u']

 

Before criticising, please READ THE QUESTION.

Share this post


Link to post
Share on other sites

I get "No" for the first one, because friction and force caused by gravity are equal.

 

I get 0.36 as the coefficient of friction between the two blocks.

 

And yeah, just draw a free body diagram. I've never done a question like this either, but its not that hard.

 

edit: Well its not hard if I get it right.

Share this post


Link to post
Share on other sites
']I get "No" for the first one' date=' because friction and force caused by gravity are equal.

 

I get 0.36 as the coefficient of friction between the two blocks.

 

And yeah, just draw a free body diagram. I've never done a question like this either, but its not that hard.

 

edit: Well its not hard if I get it right.[/quote']

 

Even without doing the question I can tell you've got it wrong, because if it moves or not is independent of the mass.

 

You can't have it not moving for a. at 0.25, then say the minimum for it to not move is 0.36 for b., as 0.25 < 0.36. Either it moves and b is greater than 0.25 or it doesn't move and b is less than or equal to 0.25.

 

You got b right, though (tan 20).

Share this post


Link to post
Share on other sites
Even without doing the question I can tell you've got it wrong' date=' because if it moves or not is independent of the mass.

 

You can't have it not moving for a. at 0.25, then say the minimum for it to not move is 0.36 for b., as 0.25 < 0.36. Either it moves and b is greater than 0.25 or it doesn't move and b is less than or equal to 0.25.

 

You got b right, though (tan 20).[/quote']

 

Oh yeah I see what I did, I just mixed Fp and Fn around because I was just writing down numbers wherever I could find space on the page.

 

Hmm, but would you have to add the 8kg mass to the 10? I guess you probably would, since it does add to the wieght.

Share this post


Link to post
Share on other sites

You don't actually need to know the weight you're dealing with.

 

slopeythang.jpg

 

Resolving perp to plane:

 

R = mg cos 20

 

Resolving // to plane, P being the resultant force down the slope:

 

P = mg sin 20 - mu * R

 

= mg sin 20 - 0.25 mg cos 20

 

= mg (sin 20 - 0.25 cos 20)

 

= mg (THE ONE CALCULATION! 0.34 - 0.23 (2sf))

 

P > 0, therefore there is a resultant force down the slope, therefore the block will move (Newton II)

Share this post


Link to post
Share on other sites
Guest Corpuscle

You're quite the artist there Jaikiri

Share this post


Link to post
Share on other sites
You're quite the artist there Jaikiri

 

I am a man of endless talent, obviously.

Share this post


Link to post
Share on other sites
What program did you use to draw that pretty diagram, Jakari?

 

MSPaint, king amongst the drawers of stupid diagrams.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
Sign in to follow this  

×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.