Where Am I Going Wrong in Calculating Minimum Coefficient of Friction?

[ehild]

It is zero. Do you see any difference between plus zero and minus zero?

 

[ehild]

friction force= -0?

It is zero. Do you see any difference between plus zero and minus zero?

 

[gracy]

Do you see any difference between plus zero and minus zero?

No.Not at all.Just edited.

 

[gracy]

But how I will get 0.75 more than or equal to coefficient of friction then?The answer should be 0.75.

 

[gracy]

The answer should be 0.75.

Just have a look at first question
http://www.educationguru4u.com/Pages/EasyPhysics.aspx

 

[ehild]

Just have a look at first question
http://www.educationguru4u.com/Pages/EasyPhysics.aspx

I see. Then my drawing was wrong, why did you say it was correct ?
Draw the FBD for the small block.

 

[gracy]

Then my drawing was wrong,

WHY?

 

[gracy]

Was the block M a wedge?

 

[gracy]

why did you say it was correct ?

I thought It is just 2 blocks on inclined surface as my title indicates.

 

[ehild]

In physics problems, block is meant that : http://www.wdlconcrete.co.uk/images/blockmain-dense-midi.jpg

 

[gracy]

So how that's going to change your answer?from zero to 0.75?please I have to finish this as soon as possible.I have many other problems to solve.

 

[gracy]

I see. Then my drawing was wrong, why did you say it was correct ?
Draw the FBD for the small block.

 

[BvU]

Picture looks awful still. m is lying on a horizontal surface. Picture in link is fine and under 1 in post #1 is hmmm.

So back to post #3 by Chet: three forces working on m have to result in an acceleration $g\sin\theta$ along the plane.
Draw the diagram and calculate the forces.

The $\tan\theta$ answer is correct.

 

[Chestermiller]

Gracy,

Are you saying that you see no difference in the figure ehild drew in post #12 and the figure in the link that you yourself presented in post #40, and that they should have the same answer?

Chet

 

[ehild]

View attachment 80831

I help with a new picture, as nothing can be seen from yours. Note that m is on a horizontal surface!

 

[gracy]

From where mg sin theta is coming?component of mg?

 

[ehild]

From where mg sin theta is coming?component of mg?

It is the resultant force on m. You know that it accelerates down the incline with a= gsin(37), so the resultant force is ma= mgsin(37).

 

[gracy]

I see. Then my drawing was wrong, why did you say it was correct ?

In physics problems, block is meant that : http://www.wdlconcrete.co.uk/images/blockmain-dense-midi.jpg

But the link I have provided i.e http://www.educationguru4u.com/Pages/EasyPhysics.aspx says M is also a block.

 

[ehild]

But the link I have provided says M is also a block.

Yes, but a wedge was drawn, and the solution they provided counts with the wedge.

 

[gracy]

Yes, but a wedge was drawn

You mean question is wrong?

 

[ehild]

In wider meaning, block can mean other shapes.
a. A solid piece of a hard substance, such as wood, having one or more flat sides.
b. Such a piece used as a construction member or as a support.
c. Such a piece upon which chopping or cutting is done: a butcher's block.
d. Such a piece upon which persons are beheaded.
e. One of a set of small wooden or plastic pieces, such as a cube, bar, or cylinder, used as a building toy.

So solve the problem according to the original figure. The top surface of M is horizontal, as in your second figure in the OP.

 

[gracy]

How your post 50 gives answer 0.75?Please answer.

 

[BvU]

In PF it's good habit that we help as much as we can, but do not do the exercise for the poster. You wouldn't let someone else train in your place if you want to run a marathon, would you ?

So back to post #3 by Chet: three forces working on m have to result in an acceleration gsinθ g\sin\theta along the plane.
Draw the diagram (that's done now) and calculate the forces.

 

[gracy]

I have done really hardwork on this particular question,that's why I was expecting that I will be understood that inspite of so much try she is not getting let's help her one step ahead by providing complete solution of the question..But no problem .

 

[gracy]

Actually I am running out of time.

 

[Chestermiller]

Actually I am running out of time.

How much time does it take to resolve a vector into two components, one horizontal and the other vertical?

Chet

 

[gracy]

How much time does it take to resolve a vector into two components, one horizontal and the other vertical?

I have done this but not getting answer.

 

[Chestermiller]

I have done this but not getting answer.

Well tell us what you get for the two components of the acceleration.

Chet

 

[ehild]

I have done this but not getting answer.

I do not see that you gave the horizontal and vertical components of the force F=mgsin(37). Recall that force is parallel with the incline, so makes 37°angle with the horizontal.