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1. Differential equations help!

OH MY GOD. there goes 20 points that i should of gotten. thank you for the helpe.
2. Differential equations help!

Homework Statement this problem was on my finals and i stared at it for 30 mins straight and still didn't figure it out and now it just bothers me that i don't know how to do the first problem on my final exam. "find the general solution to the dfq" xy'+xy= 1-y Homework Equations...
3. Nonhomogeneous diff equations method of undeterined coeff.

Thanks alot HallsofIvy, it seems i just subbed in wrong for y''p and the "c" ended up canceling out anyways.
4. Nonhomogeneous diff equations method of undeterined coeff.

thanks for responding, Lets see if i have the yp's correct yp = (At^2+Bt+c)e^-t y'p = (2At + B)e^-t -(At^2+Bt+c)e^-t y''p = 2Ae^-t - (2At + B)e^-t - (2At+B)e^-t -(At^2+Bt+c)e^-t
5. Nonhomogeneous diff equations method of undeterined coeff.

Homework Statement Find the general solution to the diff equation using undetermined coefficients y''-2y'-3y = 3te^-1 Homework Equations The Attempt at a Solution r^2 - 2r -3 = 0 r = -1, 3 so y = c1 e^-t + c2e^3t + yp since e^-t already exists as a solution, i have to...
6. Differential Equations reduction of order

Homework Statement Find y2 given t^2y'' + 3ty' + y = 0 y1(t) = 1/t Homework Equations The Attempt at a Solution i found y, y' and y'' and plugged it back in to the Differential equation, after doing some work, i'm basicly down to tv''+v' = 0 where y2 = v/t so u =...
7. Integrating factor confusion

oh wow i thought u could bring the 2 out front.... thanks for clearing that up
8. Integrating factor confusion

Homework Statement Solving this differential equation ty' + 2y = t^2 - t + 1 Homework Equations Its linear so i set it up in linear form y' + y(2/t) = t - 1 +1/t The Attempt at a Solution the integrating factor (u) = e ^ integral (ydt) = e^ integral (2dt/t)... Here's the...
9. Floating bed problem

Homework Statement There is a large bed floating in sea with the density of 765 kg/m^3. What fraction of the bed's volume will be under the surface of the water? The density of sea water is 1035 kg/m^3. Homework Equations Fb = Density * v * gravity The Attempt at a Solution I know...
10. Block on a roller coaster

I got it! i didn't know that it was still a conservation problem. thanks alot for the help
11. Block on a roller coaster

oh crap posted wrong part >.< The block's suppose to be "A uniform solid cylinder (m=0.450 kg, of small radius)" and answer's 6.00m/s. Sorry.
12. Block on a roller coaster

Homework Statement A small cube (m=0.450 kg) is at a height of 393 cm up a frictionless track which has a loop of radius, R = 58.95 cm at the bottom. The cube starts from rest and slides freely down the ramp and around the loop. Find the speed of the block when it is at the top of the loop...
13. Weight in water

Ahh i see what i did thank you all for the help
14. Weight in water

Ok, now ill sound just plain stupid. How do i find the density of water?
15. Weight in water

Isn't that what i did? B = Density * V * g and like you said water is fairly constant, so V = B/g which is 34N/9.8 = 3.47 which is the volume of the object, right? So now i can do D = m/v for the density of the object given m of object is 341/9.8. And i just confused myself, we're ignoring the...
16. Weight in water

Homework Statement An object weighing 341 N in air is immersed in water after being tied to a string connected to a force scale. The scale now reads 307 N. Calculate the density of the object. Homework Equations Fb=(density of the surrounding liquid)(V)(g) The Attempt at a...
17. Diameter of a wire

Sorry for not replying earlier... fell asleep. I used 9.81 as g, and idk what the right answer is... =(
18. Diameter of a wire

Homework Statement Find the minimum diameter of an l = 17.2 m long steel wire that will stretch no more than 7.38 mm when a mass of 323 kg is hung on the lower end. (Hint: The Young's modulus of steel is 200.0 GPa.) Homework Equations Youngs = (Force / Area) / (change L / L)...
19. Damped Oscillator and time

OK i'm retarded. n = 7.47 My friend here said not to do .96squared and woulnd't tell me why. So i blame her. Thanks again =D
20. Damped Oscillator and time

i got 16.97 as n. it works because .96^17 = ~ 0.499 So if thats true, 0.88 which is the period * 16.97 which gives me 14.94 seconds. This makes sense except the answer's still wrong?
21. Damped Oscillator and time

Homework Statement A mass M is suspended from a spring and oscillates with a period of 0.880 s. Each complete oscillation results in an amplitude reduction of a factor of 0.96 due to a small velocity dependent frictional effect. Calculate the time it takes for the total energy of the...
22. Potential Grav. Energy to Kine. Energy Problem

i see. I got 85000, which was right. Thanks again
23. Potential Grav. Energy to Kine. Energy Problem

Homework Statement On a roller coaster ride the total mass of the cart - with passengers included - is 280 kg. Peak K is at 46.0 m above the ground, peak L is at 21.5 m. The speed of the cart at K is 17.1 m/s, at L it is 12.8 m/s. How much energy is lost due to friction between the two peaks...
24. Sliding down a Track, loop, Conservation problem

I don't think that works. Remember gravity is still pulling on the block as it travels up the loop, so the speed has to be different from when it entered the loop. I believe it has something to do w/ conservation of energy, i just don't know where to start
25. Sliding down a Track, loop, Conservation problem

Homework Statement A small cube (m=0.450 kg) is at a height of 393 cm up a frictionless track which has a loop of radius, R = 58.95 cm at the bottom. The cube starts from rest and slides freely down the ramp and around the loop. Find the speed of the block when it is at the top of the loop...
26. Sphere rolling down a ramp problem

i hate when they put extra information in it, you just feel obligated to use it. yes your right, thanks alot for the help!
27. Sphere rolling down a ramp problem

Ops... forgot to add the question. silly me >.<
28. Sphere rolling down a ramp problem

Homework Statement A solid sphere of uniform density (weight = 3.2 lbs starts from rest and rolls down a ramp (H = 1.57 m, q = 18.3°.) Find the speed of the sphere's CM when it reaches the bottom of the ramp. haha sorry bout that.... Homework Equations see below The Attempt at...
29. Four mass and Tension problem

Yeah, your right. someone on my online class said to consider A and B as a whole but i guess thats wrong. thanks again!
30. Four mass and Tension problem

Homework Statement Four blocks are on a horizontal surface. The blocks are connected by thin strings with tensions Tx, Ty, Tz. The masses of the blocks are A=22.0 kg, B=21.0 kg, C=17.0 kg, D=27.0 kg. Two forces, F1=83.0N and F2=50.0N act on the masses as shown. Assume that the friction...