# Homework H.4.C ## 17 thoughts on “Homework H.4.C”

1. hu665 says:

For all questions, do we consider g=9.8 or g=-9.8?

1. ecasetti says:

I think it depends on what they call the vertical axis and how you orient it. So if you have a regular Cartesian x and y axis, gravity would be -9.8 because it is in the negative direction, but if your coordinate system is upside down, then it would be a positive value.

2. Paul V Richards says:

How do we find the tensions in the ropes in terms of given quantities?

1. ecasetti says:

I wrote the x and y equations for both blocks, then found all of the tensions in terms of one tension (I used to the tensions between block A and the pulley C). Then you can substitute so you only have tension, force, and mass left. Then plug it into F=ma.

3. Jack Christiansen says:

Would it be sensible to place the coordinate axes such that the x-axis is parallel to the incline?

1. ecasetti says:

Yeah, that's what I did. It requires a lot less trig that way!

4. czt says:

What terms, at most, do we leave the answer in?

1. ecasetti says:

I think you only need m, g, and F.

2. Matthew Torrisi says:

If you orient the coordinate system so that the x is parallel with the inclined surface, then just m,g, and F. But if you leave the system parallel with the diagram, then you'd need theta as well.

3. kberdin says:

Since they didn't specify in the instruction I left my final terms in F,m, and g.

5. Chick-fil-A Official says:

I placed the coordinate system x parallel with the incline, and i still got theta in my answer. Are we supposed to have theta in the accelerations of block A and B?

1. Qianyu Zhao says:

Be confident if you considered the contribution of gravitational force in your Newton’s equation.

2. CMK says:

Yes, θ will appear in your final answers - the accelerations of the blocks do depend on the angle of the incline.

6. Flynn Botkin says:

Is the effect of the pulleys that A is holding 1/4 of the weight of B and B is getting 1/4 the effect of F, or is it more complicated than that?

1. Elijah P Moss says:

I believe it is more complicated than that. Since block A has a net acceleration, F is not necessarily equal to the tension on pulley A.

7. Ethan Chu says:

Is there a need for the length of each of the pullies because the cable is not one continuous piece?

8. Yes says:

Do we have to use s to solve this?