Angular acceleration Definition and 566 Threads

In physics, angular acceleration refers to the time rate of change of angular velocity. As there are two types of angular velocity, namely spin angular velocity and orbital angular velocity, there are naturally also two types of angular acceleration, called spin angular acceleration and orbital angular acceleration respectively. Spin angular acceleration refers to the angular acceleration of a rigid body about its centre of rotation, and orbital angular acceleration refers to the angular acceleration of a point particle about a fixed origin.
Angular acceleration is measured in units of angle per unit time squared (which in SI units is radians per second squared), and is usually represented by the symbol alpha (α). In two dimensions, angular acceleration is a pseudoscalar whose sign is taken to be positive if the angular speed increases counterclockwise or decreases clockwise, and is taken to be negative if the angular speed increases clockwise or decreases counterclockwise. In three dimensions, angular acceleration is a pseudovector.For rigid bodies, angular acceleration must be caused by a net external torque. However, this is not so for non-rigid bodies: For example, a figure skater can speed up her rotation (thereby obtaining an angular acceleration) simply by contracting her arms and legs inwards, which involves no external torque.

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  1. S

    Angular Acceleration vector help

    Im a fairly new to physics and I have a homework question off mastering physics which is , A wheel is spinning at 43rpm with its axis vertical. After 15 sec , it's spinning at 61rpm with its axis horizontal. Find (a) the magnitude of its average angular acceleration and (b) the angle the average...
  2. N

    Find the Angular Acceleration with and Without the disk inertia

    Homework Statement Determine the angular acceleration of the uniform disk if (a) the rotational inertia of the disk is ignored and (b) the inertia of the disk is considered. The system is released from rest, the cord does not slip on the disk, and bearing friction at O may be neglected. The...
  3. S

    Torque on a wheel and angular acceleration.

    So, torque is given by I (moment of inertia) x angular acceleration. Let's say that the wheel is a hollow cylinder so the M.O.I is mr^2, I think. If a torque, T is applied to the wheel and there is a frictional force acting on the wheel, calculate the angular acceleration. Well, T - r(F) = I x a...
  4. F

    Torque and angular acceleration of two discs

    Homework Statement Homework Equations Ʃ\tau = I\alpha ƩF = ma The Attempt at a Solution I was able to calculate A and B which I am confident is correct.. for part C is what I'm having trouble with. Since both disks are fixed together, does that mean they share the same...
  5. A

    How Do You Calculate Average Angular Acceleration with Axis Orientation Change?

    A wheel is spinning at 44 with its axis vertical. After 15 , it's spinning at 60 with its axis horizontal. Find (a) the magnitude of its average angular acceleration and (b) the angle the average angular acceleration vector makes with the horizontal. Just trying to work out what I'm doing wrong...
  6. N

    Calculate the Tension and Angular Acceleration in Log After Release

    Homework Statement The uniform 69-lb log is supported by the two cables and used as a battering ram. If the log is released from rest in the position shown, calculate the initial tension induced in each cable immediately after release and the corresponding angular acceleration α of the cables...
  7. Sneakatone

    How to find angular acceleration

    a)t=0 t=7 190/60*2pi=19.8 2950/60*2pi=308 308/7=41 I don't know what to do with acceleration with t=0. b)for tangental I used the equation alpha*R for centripetal I used...
  8. Sneakatone

    Finding angular acceleration from deceleration

    a-c are correct but I don't know how to find part d. d)when turned off, it decelerates to a stop in 39s. What is its average angular acceleration during this time? I treated this part as part c to just find angular acceleration like normal. 371.75 rad/s / 39s=9.51 rad/s^2. should it be...
  9. F

    Angular acceleration caused by mass over a pulley

    The method I'm using in the image is the one that makes the most sense to me, but I've tried others and still cannot get at the stated answer, which is 2.65 rad/s^2
  10. R

    Rate of change of angular acceleration?

    I am calculating the time it takes for an object to fall 90° about an axis of rotation in the x-y plane. I have managed to calculate the rate of change of angular acceleration, which will be represented by the symbol ψ. Unfortunately it is not rad/s^3, but (rad/s^2)/θ or \alpha/θ. The value of ψ...
  11. R

    Angular acceleration of a beam?

    This problem is making me want to tear my hair off. I am trying to calculate the time it takes for a beam to fall to the ground. http://myweb.lmu.edu/gvarieschi/chimney/Graph1.JPG It would be great if I could calculate the rate of change of angular acceleration, as the acceleration would...
  12. P

    Moment of inertia and angular acceleration

    Homework Statement If the fall height of the mass is doubled, the angular acceleration of the wheel will a. decrease by an unkown amount b. remain unchanged c. decrease by a factor of 2 d. increase by an unknown amount e. increase by a factor of 2 Homework Equations The...
  13. V

    Using gradient values of a graph to determine angular acceleration

    Homework Statement I recently conducted an experiment to determine the moment of inertia of a disc using a tachometer attached to a disc marked with reflected strips, a weight, and an oscilloscope. The resulting oscilloscope data was plugged into fitplot to generate a graph of voltage...
  14. P

    Constant angular acceleration problem

    Ok so here is the problem A centrifuge operates at 3600 rpm. When switched on it rotates 72 times before reaching operational angular speed. Find the constant angular acceleration while its speeding up. Ok so I already know I needed to convert rpm to rad/sec which I did. I'm stuck here...
  15. L

    Angular acceleration, density question

    Homework Statement First question: "A DVD player can exert a torque on a DVD of 10−3 N⋅m. What is the DVD’s angular acceleration in rad/s2? Details and assumptions The DVD has a mass of 0.015 kg and a radius of 0.06 m. A DVD can be modeled as a thin uniform cylinder. " Second question: "A...
  16. N

    Calculating Angular Acceleration of a Pulsar

    Hi everyone! I have a question about tangential acceleration: A pulsar is a rotating neutron star which sends out radio pulses with precise time intervals. Every time the star rotates a pulse is received. The period, T, is measured by measuring the time intervals between the pulses. Today...
  17. E

    How to determine the angular acceleration using the right hand rule?

    How to determine the angular acceleration using the right hand rule?? I know how to get the direction of angular velocity using RHR. We curl up our fingers to the direction at which the object rotates relative to an aix and the thumb shows the direction. My question is, with the same analogy...
  18. C

    Angular Acceleration of toy train

    Hi, thanks for taking a look! A toy train rolls around a horizontal 1.4-m-diameter track. The coefficient of rolling friction is 0.12. (a) What is the magnitude of the train's angular acceleration after it is released? (b) How long does it take the train to stop if it's released with an...
  19. L

    Angular acceleration and displacement problem

    I've listed the whole problem because I know I'll have more questions, but all I want to know atm is whether I'm plugging the right values into the equation. Thanks in advance for your help. Homework Statement A compact disc speeds up uniformly from rest to 5200rpm in 620rad. The disc’s...
  20. L

    Inelastic collision angular acceleration problem

    Having problem with task b). Any suggestions?
  21. Saitama

    Angular acceleration of the bar

    Homework Statement (see attachment) Homework Equations The Attempt at a Solution I haven't yet attempted the b) and c) parts. Part a) for the case i): When the spring 2 breaks, the rod should rotate about the point A and the only torque acting is due to weight of bar. (α is the...
  22. P

    Calculating Angular Acceleration of Wheel of Radius R Given Vector of Tot. Acc.

    How may I calculate the angular acceleration of a wheel of radius R given that its vector of total acceleration of a point on its perimeter forms an angle of pi/6 wrt the tangential acceleration at that point at t=1sec after the body has begun its motion? My attempt at a solution: a_tot =...
  23. P

    Tangential acceleration given radius and angular acceleration

    radius is 2 meters and angular acceleration is 3. How do i find the tangential acceleration?
  24. F

    Angular acceleration in terms of angular velocity

    I've been working on problems that deal with pendulums and I've noticed that a few of my answers require me to find the angular velocity, frequency, period of a pendulum. I managed to get the answer right every time, but there's a step that I didn't understand, namely converting angular...
  25. C

    What creates the angular acceleration in a pulley?

    Looking at the free body diagram of a fixed pulley with a rope going over the top half, the diagram would show tension going downward on either side and an anchor going up equaling twice the tension. I understand this is this case so the pulley doesn't move in any rectilinear motion. However...
  26. L

    Angular Velocity and Angular Acceleration help

    Homework Statement Consider four situations: I) a fan's rotation is speeding up while going in the clockwise direction; II) it is speeding up while going in the counterclockwise direction; III) it is slowing down while going in the clockwise direction; and IV) it is slowing down while going...
  27. A

    Angular acceleration of a bucket attatched to a solid cylinder

    Homework Statement This was a question from my homework. I got it wrong, even after asking my professor about it, and even though I can't get credit for it now, I'd like to know where I went wrong if anyone can help sort me out! "Water is drawn from a well in a bucket tied to the end of a...
  28. S

    Pottery wheel, angular acceleration, and required speed

    Homework Statement a small rubber wheel is used to drive a large pottery wheel, and they are mounted so that they touch. if the small wheel has a radius of 2.01 cm and accelerates at a rate of 7.08 rad/s^2 and is in contact with the pottery wheel (24.2 cm) without slipping, find the angular...
  29. P

    Need help simplifying units of slope for an angular acceleration vs torque graph

    In a lab we conducted in class we graphed angular acceleration vs torque, and found a positive linear correlation-easy enough. However I am getting rather stuck in simplifying the units of slope in terms of Kg, m, and s... I am fairly sure this will give me that angular acceleration equals...
  30. R

    Angular Acceleration of Bicycle Wheels

    Homework Statement A wheel has bicycle of diameters 109.0 cm. The bicyclist accelerates from rest with constant acceleration to 16.3 km/hr in 16.5 s. What is the angular acceleration of the wheels? Homework Equations w=v/r alpha= w/t The Attempt at a Solution I think I'm...
  31. F

    Help needed - Spinning wheel, torque, angular acceleration.

    Homework Statement There is a spinning cylindrical wheel of mass 0.013 kg at a given constant angular velocity ωo (78.54 rad/s). The wheel instantaneously begins to decelerate at an unknown constant deceleration α. From when it begins to decelerate, the wheel spins a distance of θ (0.887...
  32. Jalo

    How much is the angular acceleration?

    Homework Statement the mass, M, of the disk is 20kg, the radius is r and the force applied, F, in the periphery of the disk is 9.8N. How much is the angular acceleration? If I add a mass (m1) of 1kg to the thread what will be the angular acceleration? Homework Equations I...
  33. S

    Calculating the Average Angular Acceleration of a CD

    Homework Statement Unlike the older vinal records which rotated at a constant ω of 33.3 rotations per minute (rpm), compact disks vary their rotation speed during the playing period. A certain CD has a diameter of 12cm and a playing time of 79 minutes. When the music starts, the CD is rotating...
  34. binbagsss

    Angular acceleration direction, rotating rigid bodies

    The direction of rotating bodies about a fixed axis. I am confused on how you should regard the the direction of mg sin x, the angular acceleration and the force exerted on the body by the axis, perpendicular to OG ( where O is the fixed axis location and G is the centre of mass of the body)...
  35. F

    Spiral motion & angular acceleration (Question)

    Hello, I'm in desperate need of some help with a problem regarding spiral motion. If a particle moves along a spiral path by degrees θ in time t with intial angular velocity ωo, can the rotational kinematic equation (θ = ωot + (1/2)\alphat2) still be applied? I'm trying to solve for angular...
  36. S

    Simple question on acceleration and angular acceleration

    Homework Statement I'm just reading a graduate level mechanics book for enjoyment/practice and I just need a push in the right direction with one of the problems. It has a cylinder that is wrapped with a string around the circular part. The string is then pulled (so the force is tangential...
  37. M

    Angular acceleration of a wheel formula

    Homework Statement What is the formula for angular acceleration, when the wheel's diameter, speed, acceleration and distance are known. Homework Equations The Attempt at a Solution
  38. M

    Angular Acceleration Using Work and Energy Principals

    Homework Statement The chain of a workshop crane is 50 m long and has a mass of 3 kg/m. It is partially wound on a drum and the effective radius from the axis of the drum to the chain centre line is 0.2 m. The drum itself, including shaft and gear wheel has a mass of 100 kg and has a radius of...
  39. E

    Solving the Slender Ladder Problem: Angular Acceleration

    The slender ladder has a mass of 10 kg. It is released from rest in the position shown. Friction at the two contact surfaces are negligible. Determine the angular acceleration of the ladder. I summed forces in the x,y direction, summed moments about the ladder's center of mass, wrote a...
  40. J

    Compact disk angular acceleration

    Homework Statement A compact disc speeds from rest to 5200 rpms in 620 rad. Diameter is 5.0cm -how many revolutions did it make in this time -what is the angular acceleration in rad/s^2 -how long does ti take to reach this speed Homework Equations The Attempt at a Solution i was able to find...
  41. J

    Is there an instantaneous angular acceleration for a conical pendulm?

    For a conical pendulum, there is an instantaneous centripetal acceleration. Does this mean there is an instantaneous angular acceleration of the pendulum towards the center?
  42. S

    Angular acceleration and Torque when rod reaches vertical position?

    Angular acceleration and Torque when rod reaches vertical position?? A rod (mass 1.30 kg, length .670 m) attached to a frictionless axis is released from rest in the horizontal position. What is the magnitude of the torque and angular acceleration when the rod has reached the vertical...
  43. W

    Angular Acceleration of a Pulley Supporting Two Hanging Masses

    Homework Statement Hi all! I'm working on a dynamics homework and have hit a wall here: "If the frictional moment at the pivot O is 2 N m, determine the angular acceleration of the grooved drum, which has a mass of 8 kg and a radius of gyration k = 225 mm. Ans: α = 0.622 rad/s^2 "...
  44. J

    Angular acceleration and angular velocity

    Homework Statement Calculate the angular acceleration and angular velocity of a 4 kg object rotating in a circle of 3 m radius in a time of 6 s. Homework Equations Angular acceleration = ω2*r Angular velocity= angular displacement/time ? The Attempt at a Solution Really...
  45. J

    What is the difference between centripetal and angular acceleration?

    So as the title says, what is the difference between centripetal and angular acceleration? I already know that there is a difference in the equations for each of the components but can someone please explain it conceptually? Please use some examples in your explanation.
  46. P

    Force Required by Rockets and Angular Acceleration

    Homework Statement To get a flat, uniform cylindrical satellite spinning at the correct rate, engineers fire four tangential rockets as shown in the figure. (Picture is attached). If the satellite has a mass of 4800 kg and a radius of 2.7m , what is the required steady force of each rocket...
  47. S

    Angular acceleration problem / 99% sure I'm doing right but getting wrong answer

    A toy car is on a circular track of radius r = .274 m. The car starts at initial speed vo = 1.09 m/s, and accelerates at a constant rate to final speed vf = 2.99 m/s while making 0.507 complete revolutions around the track. What is the angular acceleration? Here is what I did: distance...
  48. J

    Angular acceleration and angular velocity

    Homework Statement Calculate the angular acceleration and angular velocity of a 4 kg object rotating in a circle of 3 m radius in a time of 6 s. Homework Equations The Attempt at a Solution Angular acceleration = ω2*r C=2∏r= 2*3.14*3=18.84 360°/57.3°=6.28 rad/s 6.28/6=...
  49. E

    Angular acceleration without rotation?

    If rod BD is fixed at collar C, it is not rotating, correct? Why is the angular acceleration being asked if it's not rotating?
  50. K

    A wheel rotates with a constant angular acceleration of 3.30 rad/s2.

    A wheel rotates with a constant angular acceleration of 3.30 rad/s2. Assume the angular speed of the wheel is 2.45 rad/s at ti = 0. (a) Through what angle does the wheel rotate between t = 0 and t = 2.00 s? Give your answer in radians and revolutions. (b) What is the angular speed of the...
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