# Search results

1. ### Pressure of person on chair Question

Use the total area of the legs. The weight is distributed over the 4 legs.
2. ### Question from simple lens diagram (camera)

Now you have the opposite problem. There's a negative sign in this one. m= -v/u The image gets flipped upside down. This happens with your eyes too; your brain flips the image back right side up.
3. ### Divergence of magnetic flux density

2 year old topic. I don't think it's relevant anymore.
4. ### Question from simple lens diagram (camera)

That looks right. The negative image distance you got before implies that the film needed to be outside the camera to capture the image.
5. ### HELP! on tension and work!

This is a 2 and a half year old topic.:wink:
6. ### Question from simple lens diagram (camera)

Why did you reason that the image distance was negative?
7. ### So, very amateur question regarding element combinations

You can have different compounds like ionic or organic and they have two different naming schemes.
8. ### So, very amateur question regarding element combinations

Yup. http://www.fairbornchempage.com/Resources/Prefixes.htm Yes. The term you were probably looking for was "chemical nomenclature" for the Google search. But you also need to know the different types of molecules to know how to name them.
9. ### Rotational kinematics check please.

θ=ω_0 t+1/2 αt^2 then n=theta/2pi θ=0.5*pi*0.2+.5*1.8*pi*.04=pi(0.1+0.036)=0.136*pi θ/2*pi=0.136*pi/2*pi=0.136/2=0.068 rev
10. ### Rotational kinematics check please.

a) correct b) still incorrect c) correct, m/s (rads are kind of like a place holder unit in this case so it goes away, i don't know the actual reason why though) d) correct, m/s2 (for same reason)
11. ### Rotational kinematics check please.

a) You didn't convert the units of ω0. b) Wrong for same reason as a. c) Wrong for same reason as a. d) Can you show the calculation? You know what your doing, just didn't convert.
12. ### If dy/dt = ky and k is a nonzero constant, y could be

Look at the derivative of e^kt and see how that relates to e^kt.
13. ### Rotational kinematics check please.

No, angular acceleration is 0.9 rad/s2. ac=vt2/r at=\alphar
14. ### Quadratic Equations and kinetics

Those are the only variables you need to know. I edited my above post, sorry for reposting what you knew.

16. ### Rotational kinematics check please.

Yea those are the answers I got as well. Resultant vector depends on the tangential and centripetal accelerations.
17. ### Rotational kinematics check please.

I don't think you're calculating them correctly because they agree with the values I got which do not agree with your values.
18. ### Suspended object moment of inertia

If you set the surface of the water to h=0 then there will not be any remaining potential energy when the bucket hits the water.
19. ### Rotational kinematics check please.

B is right, the rest are wrong.
20. ### Component vectors positive or negative and angles positive or negative

Towards the left of the y-axis is -x direction and right of the y-axis is +x direction. So the x-component of one of the vectors is negative. Which one is it?
21. ### Rotational kinematics check please.

Angular acceleration is constant. How did you end up with the 5.5 value?
22. ### Incline moment of inertia.

If they ask you for the torque you need to know the radius. In this case you just used the definition of torque without having to calculate torque itself. Problems sometimes give extra information to force you to think about what it useful info and what is not useful.
23. ### Incline moment of inertia.

Yes, the moment of inertia formula for a disk and a cylinder are the same as long as the axis of rotation is through the center.
24. ### Distance of object/lens

It states it is behind a 56mm focal length lens. Not 68mm behind the focal length of a 56mm focal length lens.
25. ### Distance of object/lens

Why is di=68+56?
26. ### Mechanical energy/efficiency problem

Yes, now how does that relate to work in and finally, work out.
27. ### Mechanical energy/efficiency problem

Work is Joules/s. 580 kg/s fall off the dam. So work in is the energy associated with the mass that falls each second. What's the energy associated with the mass?
28. ### What is the definite integral of 1/(36+x^2) with bounds [0, 6]

Well, 1/6*tan^-1(1)-1/6*tan^-1(0)=1/6*tan^-1(1)-0=1/6*tan^-1(1). So I guess you would need to know that tan^-1(1)=\pi/4.
29. ### Mechanical energy/efficiency problem

This problem looks familiar did you post it on some other message board? As you stated the mechanical energy is the ratio of the work out to the work in. What's the work in? The efficiency is 55% so, 55% of the work in is returned.
30. ### Tangent Line and Coordinates of Trigonometric Function

Nothing needs to be done with \sqrt{2}, it is a constant. What's the derivative of a constant? (btw, \sqrt{2} is an irrational number which is why you couldn't rationalize it.) The coordinates are the x and y-values of the function and y=f(x) so, (x,y)=(x,f(x))
31. ### What is the definite integral of 1/(36+x^2) with bounds [0, 6]

U substitution isn't needed. Look at an integration table. Hint: The function being integrated takes the shape of 1/(x2+a2)
32. ### Angular Momentum - quick question

Angular momentum is a vector. Flipping its direction has the effect of changing its sign in the equation.
33. ### Check simple inequality proof

Looks good. The only thing that I would change is "Assume a < b and c < d". Assuming something does not mean it is necessarily correct as a proof by contradiction can demonstrate. So you can change it to something like "Stated a < b and c < d." Since a < b and c < d was given to you.
34. ### Verification: Hanging mass on cylinder. Moment of inertia

They could be giving you extra info for you to sift through and see what's relevant and what's not.
35. ### Row equivalence

That's what I can't get around with this problem. Would the context come from what he did in class?
36. ### Vector space

There you go guys. I said it was improper because of the notation, then I took it back. Sorry to offend you guys by saying something stupid.
37. ### Inclined plane moment of inertia

First sum up all of the forces for the block. \SigmaFx=sin\theta*Fg-Ff-T=ma Then get the pulley \Sigma\tau=I*\alpha
38. ### Inclined plane moment of inertia

Use the relationship \alpha=a/r and solve the torque equation for a.
39. ### Row equivalence

So it's false because row operations can be carried out on a derived row equivalent row echelon matrix to produce another row equivalent row echelon matrix.
40. ### Vector space

I said S was an improper subset.
41. ### Vector space

Look at post #3, which has been said a few times now.
42. ### Vector space

Then it is false. There is one vector that S can exclude yet still retain it's subset status. Think of the definition of a vector space.
43. ### Vector space

S is defined as an improper subset of V; so if V is a vector space, S must be as well.
44. ### Row equivalence

Your reasoning is incorrect. Any identity matrix can be multiplied by a scalar to produce a singular, row equivalent matrix.
45. ### Row equivalence

When you say it is unique do you mean there is a one-to-one relationship with every matrix to it's reduced echelon form or that there is only one reduced echelon form for any matrix?
46. ### Find the area between two curves - Help finding the limits of integration

Perhaps this would be useful. xm*xn=xm+n
47. ### Find the area between two curves - Help finding the limits of integration

I don't know how to do with algebra but, here's a hint: What two numbers can be raised to any power and still equal themselves?
48. ### Spanning set

\mathbb{R}^n is an n-dimensional vector space. {x1,x2,...,xn} is a spanning set of \mathbb{R}^n of length n. This makes {x1,x2,...,xn} a basis of \mathbb{R}^n, which means it must be linearly independent.
49. ### Find the general solution

yp=c3x2e-2x yp=(5/2)x*x2e-2x yp=(5/2)x3e-2x
50. ### Find the general solution

(D2+4D+4)(c3x2e-2x) = 5xe-2x c3(4x2e-2x-8xe-2x+2e-2x+4(2xe-2x-2x2e-2x)+4x2e-2x) = 5xe-2x Every thing but c3(2e-2x) reduces to zero c3(2e-2x)=5xe-2x c3=(5/2)x