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.

Find the weight component acting on Block 2.

Start by drawing a free-body diagram.

Start by drawing a free-body diagram.

 

Ding ding ding.

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?" ..........

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.

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.

']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).

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.

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

 

 

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)

You're quite the artist there Jaikiri

You're quite the artist there Jaikiri

 

I am a man of endless talent, obviously.

What program did you use to draw that pretty diagram, Jakari?

What program did you use to draw that pretty diagram, Jakari?

 

MSPaint, king amongst the drawers of stupid diagrams.