# Search results

1. ### Isotope decay, fairly simple.

The final isotope is the initial mass - 1.6. When you divide by Ao, the negative stays there, right?
2. ### Isotope decay, fairly simple.

1. Homework Statement The isotope 239Pu has a half-life of 24,100 years. After 10,000 years, a sample of the isotope is reduced 1.6 grams. What was the intial size of the same (in grams)? How large was the sample after the first 1,000 years. Round your answer to four decimal places. 2...
3. ### Evaluate the integral using the integration limits

1. Homework Statement (Between 0-3) ∫x3/√(x2+9) 3. The Attempt at a Solution I attempted U sub, but that didn't work. Neither did integration by parts; however, I do remember my teacher using a method involving sub'ing an "x" or something. Anybody? Will edit in attempts as I search...
4. ### Integration by Parts homework assistance

Hmm okay, got it. So let's say U = x2 dU = 2x dv = xe5x2 V=1/10e5x2 Then, plug into the equation, and you get.... (x2)(1/10e5x2) - ∫(1/10e5x2)2x dx EDIT: Just got it, thanks a lot for your time :).
5. ### Integration by Parts homework assistance

1. Homework Statement ∫x3e5x2 dx 2. Homework Equations uv-∫vdv 3. The Attempt at a Solution I've tried this one a few times, but keep getting answers that are just out there. Could someone, if possible, work out just the beginning.
6. ### Simple Calculus (indefinite integral)

Knocked it out, thanks guys.
7. ### Simple Calculus (indefinite integral)

1. Homework Statement Find the indefinite integral: ∫ Cos32x Sin22x dx 2. Homework Equations None required 3. The Attempt at a Solution Lost on where to start. If someone could just start me off.
8. ### Just need an answer checked on a problem

1. Homework Statement I'd like to mention beforehand this is not my work, i'm simply just trying to understand it. I believe the answer is incorrect, could someone kindly indicate why? A spherical navigation buoy is tethered to the sea floor by a vertical cable as shown in the...

Bump!
10. ### Geosychoronous Satellites and their KE/Orbitals

1. Homework Statement Prove that the product of the kinetic energy and orbital radius of a geosynchronous satellite is constant. 2. Homework Equations Not sure on the orbital radius part KE=KE = ½mGM/R 3. The Attempt at a Solution I'm lost on where to begin. How exactly would I 'prove' it?
11. ### Integrating to determine speed as a function of time

Ohh so when you integrate that you get ln(v)?
12. ### Integrating to determine speed as a function of time

Thanks for the response Tiny-Tim :) Okay, so i follow you somewhat. F = -bv (general formula for resistive force). According to Newton's second law, F=ma which can be rewritten as F=m(dv/dt). You then equate those two, and you get m(dv/dt)=-bv. What happens after this? (dv/v) is the...
13. ### Integrating to determine speed as a function of time

1. Homework Statement 2. Homework Equations The above formulas 3. The Attempt at a Solution I'm lost on where to start with this. The object has an intial velocity in the X direction and has the resistive force of the plontons acting upon it when it lands. What exactly is...
14. ### Tricky problem worth 2 points on my final grade

Re: Tricky problem worth 2 points on my final grade :) That equation was ugly as hell hahaha. Okay, the velocity of the smaller block was 1.75 m/s the larger .8 m/s
15. ### Tricky problem worth 2 points on my final grade

Re: Tricky problem worth 2 points on my final grade :) Hmm I could give it a try. In regards to KE, 1/2Mv2= 1/2mv2+1/2Mv2 Not sure how to signify a collision above. Sorry for giving you a hard time. My physics professor isn't much a professor.
16. ### Tricky problem worth 2 points on my final grade

Re: Tricky problem worth 2 points on my final grade :) Okay, well rearranging that equation, you get 2mghv2/m. O.... Then the masses cancel out and you're left with 2gh=v2. Sqr[(2)(9.8)(.3)] = 2.619 So M hits m with a velocity of 2.619 m/s. _______________________________________...
17. ### Tricky problem worth 2 points on my final grade

Re: Tricky problem worth 2 points on my final grade :) Mgh = 1/2mv2, right? How would you know what your mass is in this problem?
18. ### Tricky problem worth 2 points on my final grade

Re: Tricky problem worth 2 points on my final grade :) Err mgh=PE 1/2kx2=Springs. 1/2m2=KE
19. ### Tricky problem worth 2 points on my final grade

Tricky problem worth 2 points on my final grade :) 1. Homework Statement 2. Homework Equations I honestly don't know how to tackle this. I think it's going to contain ƩF=mg, and some basic kinematic equations. 3. The Attempt at a Solution Where do is start?
20. ### Difference between F=kx and F=-kx

1. Homework Statement I notice that when solving for k, the book often uses a positive version of the formula. How do you know which to use? 2. Homework Equations F=kx F=-kx 3. The Attempt at a Solution
21. ### Simple work problem (ramp)

1. Homework Statement http://www.youtube.com/watch?v=cM3t6Td_rYs&feature=plcp 2. Homework Equations W=FΔrCosθ 3. The Attempt at a Solution My questions: 1) At around 2:30, when he draws out the free body diagram, I don't understand how he comes up with these Equations. For example...
22. ### A raindrop of mass 3.35x10[SUP]-5[/SUP] falls vertically at constant speed under the

Re: A raindrop of mass 3.35x10-5 falls vertically at constant speed under Force of gravity = 9.8 Displacement = 100 Cos (90) = 1 But if the net force is zero, what do we plug into F for the equation?
23. ### A raindrop of mass 3.35x10[SUP]-5[/SUP] falls vertically at constant speed under the

1. Homework Statement A raindrop of mass 3.35x10-5 falls vertically at constant speed under the influence of gravity and air resistance. Model the drop as a particle. As it falls 100m, what is the work done on the raindrop. (a) by the gravitational force and (b) the air resistance. 2...
24. ### A force acting on a particle moving in the xy plane is given by

Understood, so quick question, is the blue line the force? Then the other lines simply components of the force? Still a little lost. We want to calculate the work required to mvoe the object to the right first. Force is constant right? So would you use fΔrCosθ?
25. ### A force acting on a particle moving in the xy plane is given by

1. Homework Statement 2. Homework Equations W=∫ Fx dx 3. The Attempt at a Solution I think you gotta split this one in terms of axis. ∫(2yi + x2j) dx Pretty lost on it.
26. ### Multiplication using dot product.

Hahaha thanks, took me a while to catch that.. sadly.
27. ### Multiplication using dot product.

Could you specify? Are you referring to A.B=|A||B|Cosθ? Edit: nevermind, got it!
28. ### Multiplication using dot product.

Ahh just caught that. Replugged in the values, and still came out wrong. Work: Plugged in 90/(Sqr97*Sqr117) = .8448190756 Tan-1 (.84481....) = 40.191 degrees. Plugged that into online homework and it was wrong apparently.
29. ### Multiplication using dot product.

1. Homework Statement 2. Homework Equations Tan θ=A.B/|A|*|B| 3. The Attempt at a Solution A=4i-9j B=9i-6j A.B=-18 Magnitude of A = √97 Magnitude of B = √117 Solve that out using Cos-1 (-18/Sqr97*Sqr117) and I keep getting the wrong answer.
30. ### Pendulum like question? hmm

Come on guys :frown:. i just need to know how to find the tension and i'm good to go on part b to the end! from what I understand, the only forces acting upon the rope are those of the rope itself and gravity. i used mv^2/r + mg and I got around 13.4. my online homework keeps telling me i'm...