Check my work — 196 discussions

In 1893, George Ferris engineered the Ferris Wheel. It was 250 feet in diameter. If the wheel makes 1 revolution every 50 seconds, then h(t) = 125sin (pi/25t - pi/2) + 125 represents the height (h), in feet, of a seat on the wheel as a function of time (t), where t is measured in seconds...

Homework Statement Is y_1 = 1 and y_2 = root t solutions of the eqn: yy'' + (y')^2 = 0 ? first solution works (i already verified) 2nd solution i get this: (1/2)t^(-1) + (1/4)t^(1/4) which does not equal zero. is this correct so far? the thing that confuses me is the question...

Homework Statement Solve (x + 2) sin y dx + x cos y dy = 0 by finding an integrating factor .....M......N..... M_y (x+2)siny = (x+2)cosy N_x xcosy = cos y M_y not equal to N_x, therefore equation is not exact.. so far so good? thanks Homework Equations The Attempt at...

Verifying an integrating factor --please check my work , thanks. Homework Statement Verify that 1/y^4 is an integrating factor for (3x^2-y^2)dy/dx - 2xy = 0, and then use it to solve the equation (1/y^4)* (3x^2-y^2)dy/dx = 2xy* (1/y^4) =3x^2 / y^4 dy = 2x/y^3 dx =3x^2 / y dy = 2x...

Homework Statement solve the DE using power series about x_0 = 0 y'' + xy' + 2y = 0 so, i want a solution in form of y = [sum from n=0 to n=infinity]c_n x^n (i hope this makes sense, i don't know how to get summation symbol) y = [sum from n=0 to n=infinity]c_n x^n y' = [sum from...

Homework Statement A 6-kg bucket of water is being pulled straight up by a string at a constant speed. What is the tension in the rope? about 42 N about 60 N about 78 N 0 N because the bucket has no acceleration. Homework Equations \SigmaF=ma ma=T-mg T=ma+mg The...

Homework Statement Solve the following initial value problem. Sketch the solution and describe its behavior as t increases. y'' + 4y' + 3y = 0 y(0) = 2 y'(0) = -1 1st i solved the characteristic: r^2 + 4r + 3 = 0 r = -1 r = -3 then the general solution is; y = c_1e^-x +...

Homework Statement "find the general solution of the equation: y'' + 3y' + 2y = 0 characteristic is: r^2 + 3r + 2 = 0 solve quadratic: (r+2)(r+1) r = -2 r= -1 therefore GS of equation is: y = c_1e^-2x + c_2e^-x thanks for any help Homework Equations The Attempt at a Solution

Homework Statement (y-x^3) + (x+y^3)y' = 0 equation is convenienty already in the required form, that is M_(x,y) + N_x(x,y)dy/dx = 0 so.. M_y = 1 = N_x therefore equation is exact. Therefore I now solve... I am solving for a function, f(x,y) whose partial derivative with respect...

Homework Statement ty' + 2y = sin t (no initial conditions given) Homework Equations The Attempt at a Solution ty' + 2y = sin t y' + (2/t)y = sin t / t mu(x) = e^integ(2/t) = t^2 (t^2)y)' = integ t sin t (t^2)y = tsin t - t cos t + c y = (sin t - cos t)/ t...

Homework Statement I forgot how to do these and just need a little refreshing on how to solve these Homework Equations y' - 2y = (t^2)(e^2t) The Attempt at a Solution y' - 2y = (t^2)(e^2t) ok so my integrating factor is the value in front of y, right? so mu(x) = e^int-2 =...

Homework Statement A small object is 25.0 cm from a diverging lens as shown in the figure . A converging lens with a focal length of 11.4 cm is 30.0cm to the right of the diverging lens. The two-lens system forms a real inverted image 17.0 cm to the right of the converging lens. The...

Homework Statement a car's engine, producing a constant power, propels the car up a hill at a constant speed and down the hill at double the speed. if the coefficient of kinetic friction between the car and the road is 0.28, what is the angle of incline of the hill. assume the hill is...

Hi here is the problem: What I did was Z=[(XL-Xc)2+R2]1/2 = 5 ohm and then V/R = I = 110(2)1/2/5=31.1A For part B) I did V=L(di/dt)=-Lwsin(wt), and the peak amplitude is when sin(wt)=-1 and is 377V. Can someone tell me if what I did is right, or what is wrong? Thanks.

A heart pacemaker is designed to operate at 71 beats/min using a 8.5 microF capacitor in a simple RC circuit. What value of resistance should be used if the pacemaker is to fire (capacitor discharge) when the voltage reaches 69% of maximum? Here's what I've done (but my answer was wrong)...

three identical balls are thrown from the same height with the same initial speed...ball a is thrown horizontally, ball b is thrown upward at some angel above the horizontal and ball c is thrown at some angle below the horizontal...disregard air resistance and describe the motions of the three...

If a steel tower stands 300 m tall on an average day, 22 degrees C, how much taller is it on a hot day, 40 degrees C? The coefficient of linear expansion for steel is 11 (10)^-6/degree C. The equation for change in length of a material is (change in L) = L * α * (change in T) I know...

A mass is placed on a frictionless incline and attached to a pulley by a light string. The situation is sketched below. Rotation Test Figure 2 The incline angle, theta, is 50.0°, the mass is 4.00 kg, the moment of inertia of the pulley is 0.800 kgm2 and the radius of the pulley is 0.105 m...

I've never had to do one quite like this. Just wanted to check my work. Homework Statement 150g of water and 50g of ice are in a container made from 20.0g of aluminum. The system consisting of the water, ice and the container are at thermal equilibrium at 0C. The container is wrapped in a...

Friction and accelerarion...please check my work. a horizontal force of 200 Newtons is applied to a 55 kg cart across a 10 meter surface. If the cart accelerates at 2 meters/second squared, then what is the work done by the force of friction as it acts to retard the motion of the cart ...

can you check my work? "power series representation" is ok I figure it out.

Homework Statement A cart of mass M is attached to a spring with spring constant k. Also, a T-shaped pendulum is pinned to its center. The pendulum is made up of two bars with length L and mass m. Find Lagrange's equations of motion. I've attached the figure and my solution as a PDF. I...

can some one just check my work please Homework Statement model rocket of mass .250 kg is launched vertically with an engine that is ignited at time= 0, the engine provides 20 N.s impulse by firing for 2 sec . upon reaching its maximum height the rocket deploys a parachute and then desends...

Homework Statement A rollercoaster car and passengers have a combined mass of 1620 kgm, and they descend the first hill at an angle of 45o to the horizontal. With what force is the roller coaster pulled down the hill? Homework Equations The Attempt at a Solution Vertical force =...

A boy pulls a 14.6kg sled 12.5m at a constant speed across a horizontal floor. if the rope makes a 32.4degrees? angle with the horizontal and the coefficient of friction is .489, what is the work done by each of the forces acting on the sled? 2 days ago - 2 days left to answer. Additional...

An electron is initially at rest in a vacuum in a region where the potential is 0V. It is attracted by, and accelerates toward, a positively-charged metal plate at a potential of +12,000V. Assuming no other forces act on the electron, how fast is it moving when it hits the metal plate? Mass of...

Not sure if I am using the right technique or even using the technique correctly... http://img8.imageshack.us/img8/6346/practiceprob.th.jpg http://img44.imageshack.us/img44/8479/workedpracticeprob.th.jpg

1. A parent pushes a baby stroller from home to daycare along a level road with a force of 38 N directed at an angle of 30° below the horizontal. If daycare is 0.83 km from home, how much work is done by the parent? (38N)(cos(-30))(.83km)=27.21 J 2. You have a 0.750 kg picture frame on a...

Homework Statement A) A car of mass 1000 kg is acted on by a net force of 2500 N. What is the resulting acceleration? B) A car of mass 1000 kg pulls a caravan of mass 800 kg; the driving wheels of the car exert a force of 8000 N on the road. The total resistance to motion is 3000 N. B1) What...

Homework Statement There are 4 parts to this question. Two children are playing on a pulley system. A 65 kg child jumps of a platform pulling an 85 kg child horizontally across a platform. a) what is the maximum value for static friction to allow the larger child to begin sliding? b) Once...

i just need someone to check my awnsers and working XD thanks they get harder btw ;) 1: a) Write out the system of linear equations in variables, x,y,z represented by the augmneted matrix ( 1 2 0 5) ( 3 1 -1 0) ( 0 -2 1 2) my attempt at 1a: x...

For which positive integers k is the following series convergent? \sum(n!)^2/(kn)!attempt: use the ratio test. let Bn = (n!)2 / (kn!) let Bn+1 = ((n+1)!)^2 / (k(n+1))! then Bn+1 / Bn = ((n+1)!)^2 / (k(n+1))! * (kn)!/(n!)^2 from manipulation I got : (n+1)2 / k(n+1) = (n+1) /...

1. Homework Statement [/b] Sketch the region bounded by the curves, and visually estimate the location of the centroid. Then find the exact coordinates of the centroid: Homework Equations I don't have the answer for this problem to check my work. The Attempt at a Solution see...

Homework Statement Two masses, 3.2kg and 2.2kg are each initially 1.80m above the ground, and the massless and frictionless pulley is 4.8m above the ground. What maximum height dies the lighter object reach after the system is released? Assume it doesn't hit the pulley. Homework Equations...

Homework Statement int sinh(2x) cosh(2x) dx u= sinh (2x) du= 2 cosh (2x) 1/2 int u du 1/2 (u^2)/2 (sinh (2x))^2 / 4

Homework Statement A particle of mass 2.0 kg has position given by the vector r = (t^4 -3t^3) i + (t^3 - 9t) j + (2t -6) k (where i, j, and k are the unit direction vectors and r is given in meters and t in seconds. At what time in seconds is the particle located at the origin? For this I get...

Homework Statement A left-handed pitcher at sea level throws a baseball at a 45o angle with an initial speed of 19 m/s. The time for the ball to reach its highest point can be found from the data and known constants using which equations? Solve for the time. Homework Equations V^2 =...

I need somebody to double check my work...I think my math is wrong somewhere.. so I've been working on a spreadsheet to take some data from a vehicle's data port... and to transfer it into a Horsepower chart... basically making a street Dyno... I've gotten everything to work...

Homework Statement Alright so the problem: Find the reigon in the xy plane that is bounded by the curves: x = y^2 and 2y + x = 3 quickly solving for the y coordinates of intersection, i get y = -3 and 1 so using horizontal components i got: \int^{1}_{-3} 3-2y - y^2 and...

Homework Statement Find the acceleration of the system http://img266.imageshack.us/img266/4904/2pulleyszw9.jpg The rope is massless The mobile pulley is not massless, it weighs 20 grams. Find the accelereation of the system Homework Equations F=mg F=ma g = 9.8 The Attempt at a...

Homework Statement A bird is flying horizontally at a constant velocity of 2 m/s. 10 meters under the bird, there is a man that wants to shoot the bird. He is holding his gun at an angle of 45 degrees from horizontal. The initial velocity of the bullet is 25 m/s. When the man must open fire...

Repost with attachment >< 1. Homework Statement dy/dt + ty/(1+t^2) = t/(1+t^2)^1/2 y(1) = 2 Need to solve this initial value problem. The equation is a 1st order ODE 2. Homework Equations 3. The Attempt at a Solution I've attached my solution to the problem. Just...

Homework Statement dy/dt + ty/(1+t^2) = t/(1+t^2)^1/2 y(1) = 2 Need to solve this initial value problem. The equation is a 1st order ODE Homework Equations The Attempt at a Solution I've attached my solution to the problem. Just wondering if anyone can check my work. I...

Problem: given compact set C and open set U with C \subsetU, show there is a compact set D \subset U with C \subset interior of D. My thinking: Since C is compact it is closed, and U-C is open. Since U is an open cover of C there is a finite collection D of finite open subsets of U that...

I have to make a sample quiz for class. Can someone look these over and answer them so I can make sure my work is correct 1. The value of g at the Earth's surface is about 10 m/s2. What is its value at a distance from the Earth's center that is three times the Earth's radius? 2.Calculate...

Homework Statement The grade in a class is determined by three tests and a final exam. The final exam counts twice as much as a test. A student's three test grades are 78, 82, and 100. What does he need to score on the final exam to bring his average up to 90? Homework Equations...

Work input/output, efficient probelm, just need someone to check my work :) Homework Statement Because there is very little friction, the lever is an extremely efficient simple machine. Using a 90% efficient lever, what input work is required to lift an 18kg mass through a distance of 0.5m...

intrest rates/investment problem (pert), I just need someone to check my work:) Homework Statement 1)Cindy requires $10,000 in 3 years to return to college to get and MBA degree. How much money should she ask her parent for now so that, if she invests it at 12% compounded continuously, she...

Homework Statement when a car has traveled 100m up a 1 in 10 (sine slope) the driver stops and has a drink, he places an empty can of cola on the ground so that it can roll, the can weighs 50g and the radius of rotation k of the can is r a, calculate the energy of the can at the top and...

Homework Statement Two particles move along an x axis. Position of particle 1 is x = 6t^2 + 3t + 2. The acceleration of particle 2 is given by a = -8t and at t=0, its velocity is 20 m/s. When the velocities of the particles match, what is their velocity? Homework Equations The...