# Search results

1. ### 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...
2. ### 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...
3. ### 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.
4. ### 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.
5. ### 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...
6. ### 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?
7. ### 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...
8. ### 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?
9. ### 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
10. ### 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...
11. ### 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...
12. ### 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.
13. ### 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.
14. ### Pendulum like question? hmm

1. Homework Statement One end of a cord is fixed and a small 0.310-kg object is attached to the other end, where it swings in a section of a vertical circle of radius 2.50 m as shown in the figure below. When θ = 28.0°, the speed of the object is 9.00 m/s. At this instant, find each of the...
15. ### How fast can an object spin!

1. Homework Statement A light string can support a stationary hanging load of 27.0 kg before breaking. An object of mass m = 2.81 kg attached to the string rotates on a frictionless, horizontal table in a circle of radius r = 0.809 m, and the other end of the string is held fixed as in the...
16. ### Determine the magnitude of the contact force between the two blocks.

1. Homework Statement Two blocks of masses m1 and m2, with m1 > m2, are placed in contact with each other on a frictionless, horizontal surface. A constant horizontal force is applies to m1. a) find the magnitude of the acceleration b) determine the magnitude of the contact force between the...
17. ### Finding the possible values of a force pushing a block

1. Homework Statement 2. Homework Equations I believe the only necessary equations would be those utilized to find the X and Y components of a certain force as well as the formula used to find μs µ = ffriction/fnormal 3. The Attempt at a Solution Attempt: I'm not really...
18. ### Two forces acting upon an object.

1. Homework Statement 2. Homework Equations I assume, it has to do with components and forces so Fx = F Cos θ, and vice versa for the y component. 3. The Attempt at a Solution Well, initially, I tried to add them using unit vectors and got 40.0i + 13.0j for ƩF Solved for...
19. ### Basic friction problems

Hi guys, I have a test in 3 hours so in trying to understand static and kinetic problems utilizing mew. Here's my problem: A block of mass 3.00 kg is pushed up against a walk by a force P that makes the angle of theta = 30.0 angle with the horizontal. The coefficient of static friction...
20. ### Projectile being launched from ground level

1. Homework Statement A projectile is fired from ground level with an initial velocity of 50 m/s and an initial angle of 37°. Assuming g = 9.8 m/s^2, find: a) the projectiles total time of flight. b) the maximum height attained c) the total horizontal distance traveled d) the final...
21. ### Integration of an equation to find displacement

1. Homework Statement 2. Homework Equations Above 3. The Attempt at a Solution Okay, so I understand I need to integrate the top equation because it's velocity as a function of time. I just don't know how.
22. ### Confused on vectors.

1. Homework Statement 2. Homework Equations x^2 + y^2 = r^2 3. The Attempt at a Solution I understand everything, but the last segment. What vector B when added to vector A, gives a resultant vector with no x component and a negative y component 3.34 units in length? So 3.34 = Sqr...
23. ### A Glider of length moves through

1. Homework Statement A glider of length moves through a stationary photogate on an air track. A photogate shown in the figure below is a device that measures the time interval Δtd during which the glider blocks a beam of infrared light passing across the photogate. The ratio vd = /Δtd is the...
24. ### Time it takes for an object to hit the ground

1. Homework Statement The height of a helicopter above the ground is given by h = 2.55t^3, where h is in meters and t is in seconds. At t = 1.65 s, the helicopter releases a small mailbag. How long after its release does the mailbag reach the ground? 2. Homework Equations The above...
25. ### Evaluate a particles position

1. Homework Statement The position of a particle moving along the x axis varies in time according to the expression x = 3t 2, where x is in meters and t is in seconds. Evaluate its position at the following times. ( a) t = 2.30 s (b) t = 2.30 s + Δt (c) Evaluate the limit of...
26. ### Calculating the density of a sphere (uncertainty included)

1. Homework Statement The radius of a solid sphere is measured to be (6.30 ± 0.26) cm, and its mass is measured to be (1.81 ± 0.08) kg. Determine the density of the sphere in kilograms per cubic meter and the uncertainty in the density. (Use the correct number of significant figures. Use the...
27. ### Finding the density of a hydrogen proton

1. Homework Statement A proton, which is the nucleus of a hydrogen atom, can be modeled as a sphere with a diameter of 2.4 fm and a mass of 1.67e-27 kg. Determine the density of the proton. 2. Homework Equations As far as I know, the only required formula is D = m/v 3. The Attempt at a...