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  1. C

    Linear and Rotational Kinematics System.

    Alright Block 1: T1 - Frictional Force = m*a Block 3: m3*g - T3 = m*a Pulley 2: (1/2)m2*r*a = (T3 - T1)*r Then, T1 = m1*a + m1*g*u | T3 = m3*g - m3*a <--I plug these two into my 'Pulley 2' I then algebraically solve for a and I end up with, a = (m3*g - m1*g*u) / (0.5*m2 + m1 + m3) I...
  2. C

    Linear and Rotational Kinematics System.

    torque has units of Nm. So I need some sort of distance I take it? Would I use the radius as this distance? Would it be Torque=(T3-T1)r ? EDIT: This also doesn't seem to work. I'm feeling pretty lost at this point. =/
  3. C

    Linear and Rotational Kinematics System.

    Homework Statement A block of mass m1 = 2 kg rests on a table with which it has a coefficient of friction µ = 0.53. A string attached to the block passes over a pulley to a block of mass m3 = 4 kg. The pulley is a uniform disk of mass m2 = 0.4 kg and radius 15 cm. As the mass m3 falls, the...
  4. C

    Rotational Kinematics - Cylinder down a slope.

    I also tried using the gravitational force as the Torque. I used m*g*sin(20)=I*alpha m*g*sin(20)/I=alpha and alpha*R = a so... m*g*sin(20)*R/I=a, but this didn't work either. ------------------- I just solved this problem.
  5. C

    Rotational Kinematics - Cylinder down a slope.

    Are they the same? b/c the frictional force is a force not coming out from the CM; therefore it helps it spin? I believe it is the only other force, so they must be the same?
  6. C

    Rotational Kinematics - Cylinder down a slope.

    Homework Statement A certain non-uniform but cylindrically symmetric cylinder has mass 9 kg, radius 1.2 m, and moment of inertia about the center of mass 7.6 kg m2. It rolls without slipping down a rough 20° incline. What is the acceleration of the cylinder's center-of-mass...
  7. C

    KE of a rotational system

    Thanks, :P. It needed that constant for a disk (1/2). Thanks for your help. :)
  8. C

    KE of a rotational system

    Homework Statement A 15 kg uniform disk of radius R = 0.25 m has a string wrapped around it, and a m = 5 kg weight is hanging on the string. The system of the weight and disk is released from rest. a) When the 5 kg weight is moving with a speed of 1.7 m/s, what is the kinetic energy of the...
  9. C

    Momentum (Cannon fires at angle & recoils)

    These are the hints they give me, I just don't understand at all what to do. I now believe though that the velocity I'm finding in the x-direction is incorrect, but I'm not sure why. HELP: Because the cannon is moving, you must find the speed of the projectile with respect to the ground...
  10. C

    Momentum (Cannon fires at angle & recoils)

    q is typically the letter they use to denote theta, since I cannot input a theta symbol into my answer field. The field asks for "qground="
  11. C

    Momentum (Cannon fires at angle & recoils)

    what do you mean "Then please label the 40 degrees"? If you're implying that the answer is 40 degrees, I can assure with certainty that it isn't. I input these values into my homework online, and it returns with either an "OK" or "NO". I've tried 40 degrees, that was my first guess. =/ So...
  12. C

    Momentum (Cannon fires at angle & recoils)

    Homework Statement A circus cannon, which has a mass M = 5000 kg, is tilted at q = 40°. When it shoots a projectile at v0 = 80 m/s with respect to the cannon, the cannon recoils along a horizontal track at vcannon = 1 m/s with respect to the ground. 1. At what angle to the horizontal...
  13. C

    Conservation of Momentum and KE (bullet through a pop can)

    Hey, thanks. That makes sense, I should have been thinking that simple. It worked out, thanks again. :)
  14. C

    Conservation of Momentum and KE (bullet through a pop can)

    Homework Statement A bullet of mass 0.008 kg and initial speed 300 m/s penetrates an initially stationary pop can of mass 0.042 kg and emerges with a speed 210 m/s. What is the initial momentum of the bullet and pop can system? =2.4 kgm/s What is the final momentum of the bullet...
  15. C

    Work and Energy with centripedal acceleration and springs.

    Homework Statement The two problems below are related to a cart of mass M = 500 kg going around a circular loop-the-loop of radius R = 15 m, as shown in the figures. All surfaces are frictionless. In order for the cart to negotiate the loop safely, the normal force exerted by the track on...
  16. C

    Work & Energy (Spring and moving mass)

    alright, thx. I was trying to do that last night, but gave up when I thought all i had was one side. I just used a previous triangle to find the angle, and then used that to find x. thanks for your help, I really appreciate your input. :)
  17. C

    Work & Energy (Spring and moving mass)

    I'm not sure how I find the horizontal component of the spring force. sorry, i'm really trying to wrap my head around this, i'm just finding it difficult right now.
  18. C

    Work & Energy (Spring and moving mass)

    yeah i tried that too. I found the distance the spring stretched to be 1.9644m. (25+4.848^2=(sqrt(answer))) I then multiplied that by -k, and divided by mass, and still not the correct answer.
  19. C

    Work & Energy (Spring and moving mass)

    Alright, So I set up the force to equal -k*x (-12*4.848) and then divided this answer by 3.5kg (F/m=a). That doesn't yield the correct answer either.
  20. C

    Work & Energy (Spring and moving mass)

    the force of the push, and the force of the spring?
  21. C

    Work & Energy (Spring and moving mass)

    Homework Statement http://pyrofool.googlepages.com/picspring.gif [Broken] A block of mass m = 3.5 kg rests on a frictionless floor. It is attached to a spring with a relaxed length L = 5 m. The spring has spring constant k = 12 N/m and is relaxed when hanging in the vertical position. The...
  22. C

    Work and Energy

    oh alright thanks. I see now, that was easier than I was thinking. thanks!
  23. C

    Work and Energy

    oh, how would i calculate the velocity then, if it's not 20 N when it returns? or if i use the same formula (KE(final) - KE(initial) = W), how would I calculate that Work?
  24. C

    Work and Energy

    Homework Statement A spring is stretched a distance of Dx = 40 cm beyond its relaxed length. Attached to the end of the spring is an block of mass m = 8 kg, which rests on a horizontal frictionless surface. A force of magnitude 20 N is required to hold the block at this position. The force...
  25. C

    Friction and Constant velocity

    okay, so if I'm using it in the required direction, don't I have to use m*g*sin(theta) because gravity isn't pulling it from the side, it's pulling straight down on it?
  26. C

    Friction and Constant velocity

    okay, so I'm assuming them I will be using the static coefficient because that's the kind tires use on pavement and whatnot. For the weight force... would that be the force pulling the car down the slope? m*g*sin(theta)? or do u mean the weight force as 1000*9.81?
  27. C

    Friction and Constant velocity

    hello, yes, so i have my two frictional forces pointing upwards on the slope. I set it up like this... (1000)(9.81cos(theta))(.89)+(1000)(9.81cos(theta))(.61)-?=0 ...If this is correct, which I am not so sure b/c it just seems like I wouldn't be able to create an opposite force to equal it, so...
  28. C

    Friction and Constant velocity

    Homework Statement A car of mas m = 1000kg is sliding down a hill. The coefficients of friction between the car's tires and the ground are us=0.89 and uk=0.61. For what inclination angle will the car slide down the hill with a constant velocity? Homework Equations The Attempt at a...
  29. C

    Tension between 2 blocks and friction.

    Hey, if someone could help me. I'm really stuck on this one, I just think I've dug myself a deeper hole trying to work this out. I would really appreciate any more help. EDIT: I solved it. it's 10 N...
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