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. G

    Angular acceleration of a rotating point mass

    Hi,first time posting here, so please be gentle... I am studying a point mass doing uniform circular motion on a horizontal frictionless table with tension in a string fixed at one end as the center. Everything is clear if center of circle is treated as center of rotation 'O' for the $$\tau = I...
  2. gcombina

    Is Angular Acceleration Zero in Constant Rolling Motion?

    Homework Statement Which statement concerning a wheel undergoing rolling motion is true? (a) The angular acceleration of the wheel must be zero m/s2. (b) The tangential velocity is the same for all points on the wheel. (c) The linear velocity for all points on the rim of the wheel...
  3. gcombina

    Therefore, the angular acceleration is 3.925 rad/s2.

    Homework Statement A grindstone, initially at rest, is given a constant angular acceleration so that it makes 20.0 rev in the first 8.00 s. What is its angular acceleration? (a) 0.313 rad/s2 (c) 2.50 rad/s2 (e) 3.93 rad/s2 (b) 0.625 rad/s2 (d) 1.97 rad/s2Homework EquationsThe...
  4. R

    Why is Arc Length Calculated as r*theta in Circular Motion?

    According to what I've read, I was told that 1) s = r*theta 2) angle("theta"): theta(t) in radians 3) angular velocity ("omega"): omega(t) = d/dt theta(t) in rads/s 4) angular acceleration ("alpha"): alpha(t) = d/dt omega(t) in rad/(s^2) However I do not understand the concept of this. I...
  5. 2

    Can you have angular acceleration without centripetal acceleration?

    Homework Statement My guess is no because if you have a ball on a string, for there to be angular acceleration, the angular velocity must increase so you need an increasing tangential speed, so your centripetal acceleration must increase (α=v2/r)... but I'm not sure. One other question...
  6. K

    Angular acceleration of pulley with two masses

    1. Homework Statement The system shown in the diagram contains two blocks, of masses 1.9 kg and 5.7 kg, connected by a light string over a pulley of radius 0.15 m and rotational inertia 2.8 kg m 2 . The block of mass 5.7 kg is free to slide on a horizontal frictionless surface and the pulley is...
  7. PhysicsStudnt

    Angular acceleration and centri fugal/petal Force

    Experts, I need to find out the centrifugal acceleration on a ball of mass m placed at a distance R from one end of the rod, and that end is being pivoted to rotate the rod..Of angular acceleration is alpha, is it correct to say, Centripetal / centrifugal (in case that the ball remains...
  8. hdp12

    Angular Acceleration Caused by Axehead on a Rotating Grindstone (Disk)

    Homework Statement PROBLEM: You have a horizontal grindstone (a disk) that is mass m, has a radius r, and is turning at f in the positive direction. You then press a steel axe against the edge with a force of F in the radial direction. RANDOMIZED VARIABLES: m= 95 kg r= 0.33 m f= 92 rpm F= 25...
  9. hdp12

    Torque Causing Angular Acceleration on a Uniform Disk

    Homework Statement /* Intro, personal: I am taking Studio Physics 1 at FSU this summer semester. We have an online homework assigned weekly via a program called ExpertTA. This question has been giving me the HARDEST time and I seriously just need some help on it. I have completed and submitted...
  10. BrainMan

    Angular Acceleration and torque problem

    Homework Statement A 12 kg mass is attached to a cord that is wrapped around a wheel of radius r = 10 cm (Fig. 8.20). The acceleration of the mass down the friction-less incline is 2.0 m/s^2/. Assuming the axle of the wheel to be friction-less, determine (a) the tension in the cord, (b) the...
  11. BrainMan

    Torque and angular acceleration pulley problem

    Homework Statement A pulley in the shape of a cylinder of mass 5 kg and radius 0.6 m has a force of magnitude 30 N exerted tangentially on it. Find the angular acceleration of the pulley and its angular velocity after 3 s, assuming it starts from rest. Homework Equations T = Ftr T = mr^2a...
  12. gcombina

    How Do You Calculate Angular Acceleration from Revolutions?

    A grindstone,initially at rest,is given a constant angular acceleration so that it makes 20.0 rev? A grindstone,initially at rest,is given a constant angular acceleration so that it makes 20.0 rev in the first 8.00 s. What is its angular acceleration Answer is 3.93 rad/s^2 My attempt...
  13. BrainMan

    How Do You Calculate Average Angular Acceleration from Revolutions?

    Homework Statement A turntable moves from rest to an angular speed of 45 rev/min in 1.5 s. What is its average angular acceleration? Homework Equations ω = ωo + \alphat The Attempt at a Solution I first converted 45 to radians by multiplying it by pi 45(3.14152654)/180 = .79 rad...
  14. J

    Solving for Angular Acceleration & Speed of Rod in Freefall

    Homework Statement Consider a uniform rod of mass 12kg and length 1.0m. At its end, the rod is attached to a fixed, friction-free pivot. Initially the rod is balanced vertically above the pivot and begins to fall (from rest) as shown in the diagram. Determine, a) the angular acceleration of...
  15. P

    Angular Acceleration: 0.29 rad/s/s

    Homework Statement If a dynamometer is set to move at 180 deg/s and it takes 0.18 seconds to reach that speed. What was the angular acceleration of the test arm in radians/s/s to get to that velocity? Give your answer rounded to two decimal places and do not include units in answer...
  16. V

    Angular Acceleration of A rod with friction. Dynamics (General Plane)

    Homework Statement A 100 kg slender rod is lifted on the left end until the angle between the ground and the right end is 30 degrees. The right end is still in contact with the ground. The coefficient of friction between the rod and the ground is .5 and the length of the rod is 2.1 m...
  17. S

    Angular Acceleration of a Fixed Rod

    Homework Statement Consider a thin 14 m rod pivoted at one end. A uniform density spherical object (whose mass is 9 kg and radius is 3.2 m) is attached to the free end of the rod and the moment of inertia of the rod about an end is Irod =1/3mL^2 and the moment of inertia of the sphere about its...
  18. R

    Rocket engine gimballing - torque and angular acceleration question

    Hello Firstly i just registered, I am a final year computer science student and I am busy working on my thesis (the deadline is fast approaching) I am working this application of a rocket going into orbit and physics is not my forte. I need some help on converting the gimbal of a rocket...
  19. S

    Gravity and Angular acceleration

    Homework Statement There is strong evidence that Europa, a satellite of Jupiter, has a liquid ocean beneath its icy surface. Many scientists think we should land a vehicle there to search for life. Before launching it, we would want to test such a lander under the gravity conditions at the...
  20. J

    Calculating the angle using angular acceleration

    Hi I have calculated angular acceleration which changes with time. I also have a moment(torque) which also changes with time and a fixed moment of inertia. Is there an equation or a way for me to work out the change in angle with respect to time using this information? If not, what other...
  21. K

    Angular Acceleration and Radius

    I am writing a lab report for an experiment where we used a rotary motion sensor with different sized disks to find angular acceleration as a string attached to a falling weight unraveled and accelerated the disk. I am having confusion with my graph results and am wondering if they are correct...
  22. U

    Angular acceleration of a falling arm

    Homework Statement Assume your arm is a solid rod, 0.740 m in length, free to rotate about your shoulder (so its moment of inertia is (1/3)ML^2). If you hold your arm out sideways, and then completely relax your muscles, what is the initial downward angular acceleration of your arm? Homework...
  23. B

    Angular Acceleration (and other torque/angular problems)

    Homework Statement A thin, uniform stick of length 2.1 m and mass 3.9 kg is pinned through one end and is free to rotate. The stick is initially hanging vertically and at rest. You then rotate the stick so that you are holding it horizontally. You release the stick from that horizontal...
  24. gcombina

    Angular Acceleration Problem - Compact Disc

    During the time a compact disc (CD) accelerates from rest to a constant rotational speed of 477 rev/min, it rotates through an angular displacement of 0.250 rev. What is the angular acceleration of the CD? I converted 477 rev/min into 49.95 rad I converted 0.250 rev to radians which is 1.57 rad...
  25. applestrudle

    Is the angular acceleration of a rolling object constant?

    I understand that the torque caused by the friction must cause an angular acceleration, and it makes sense that the angular velocity increases from the bottom to the top so if there was a particle on the rim, as it went upwards it's speed would increase but what happens when it comes down again...
  26. gcombina

    Angular Acceleration Problem - The Grindstone Problem

    A grindstone, initially at rest, is given a constant angular acceleration so that it makes 20.0 rev in the first 8.00 s. What is its angular acceleration? I don't know which angular formula to use and how many are out there? I am so confused
  27. gcombina

    Calculating Angular Acceleration for a Rotating Compact Disc

    Problem(physics class 201/Portland Community College) During the time a compact disc (CD) accelerates from rest to a constant rotational speed of 477 rev/min, it rotates through an angular displacement of 0.250 rev. What is the angular acceleration of the CD? (a) 358 rad/s2 (c) 901 rad/s2...
  28. M

    What Is the Angular Acceleration and Force Exerted on a Falling Fence?

    Homework Statement A man jumps at a fence. The fence hits the ground in 0.81 seconds, and the height of the fence is 1.24 meters. What is the angular acceleration of the fence? What is the force exerted by the man on the fence? The fence has a mass of 40 kg. Homework Equations...
  29. U

    Angular acceleration, rigid body

    Homework Statement A circular disk with the mass m and radius r is hanging from two ropes with length l when suddenly the rope ED snaps. For this moment, find: a, The angular acceleration for the rope OB, the angular acceleration for the disk b, The force T acting in OB The Attempt at...
  30. AakashPandita

    Angular acceleration x radius= Acceleration of center of mass ?

    For a rotating body, (angular acceleration x radius)= Acceleration of center of mass ? But a rotating body can have angular acc. even if it is not translating. what is wrong?
  31. N

    Rotational Kinematics - Angular Acceleration

    Homework Statement A phonograph turntable with an initial angular velocity of 78 rpm continues turning for 40 rotations after being switched off. What is the angular deceleration of the turntable? Assume constant angular deceleration. Homework Equations \alpha=(\omega-\omega0)/t...
  32. T

    Angular acceleration with a mass

    Homework Statement 1) A solid cylinder of mass M = 1.54 kg and radius r = 0.100 m pivots on a frictionless bearing. A string wrapped around the cylinder pulls downward with a force F that equals the weight of a 0.590 kg mass, i.e., F = 5.782 N. Calculate the angular acceleration of the...
  33. I

    Angular acceleration of a planet

    So my teacher said that an object farther from the center experiences greater centripetal acceleration. How is that possible? let's say we have a sun + planet system. F = GmM/r^2 so when the planet's r is greater, wouldn't the force become lower compared to the planet being closer to the sun?
  34. F

    Torque and angular acceleration

    Homework Statement A massless beam is supported only at one point, called the pivot point, as shown in the diagram. A block with mass m1 sits at the left end of the beam, a distance L1 from the pivot point. A block with mass m2 sits at the right end of the beam, a distance L2 from the pivot...
  35. T

    How Do You Calculate the Angular Acceleration of an Arm?

    Homework Statement Assume that a 1.20-kg ball is thrown solely by the action of the forearm, which rotates about the elbow joint under the action of the triceps muscle, the figure. The ball is accelerated uniformly from rest to 9.5m/s in 0.38s , at which point it is released. Assume that the...
  36. L

    Problem with rotational torque and angular acceleration

    I've attached a screenshot of this particular question. I was able to figure out part A but I'm having some difficulty with part B. Relevant equations: T = I*alpha I = .5mr^2 (for a solid cylinder like the grinding wheel) F = ma Attempt at solution: I've gotten as far as setting up...
  37. N

    Mass on Pulley problem need to find angular acceleration

    Homework Statement A string is wrapped around a pulley of radius 3.45cm , and a weight hangs from the other end. The weight falls with a constant acceleration 3.00m/s2 . What's the angular acceleration of the pulley? Homework Equations i'm writing out the equations i would think that...
  38. A

    Circular Motion with constant angular acceleration

    Homework Statement An object travels counterclockwise on a circular path with radius R and constant angular acceleration α , so that vector r(t) = R cos(αt^2/2) i^+ R sin(αt^2/2) j^  Homework Equations b. Find the time T when the object made a single revolution and returned to...
  39. T

    Angular acceleration of a massless pulley

    Consider a massless string going over a massless frictionless pulley with masses M1 and M2 at the end of the string. The tension in the string would be same. The torque equation of the pulley says (T1-T2)=Iα .Now L.H.S is zero since T1=T2 and also I=0 . So,we have a condition 0=(0)(α)...
  40. B

    Linear and angular acceleration problems.

    Homework Statement A mass of 0.5kg is suspended from a flywheel. If the mass is released from rest and falls a distance of 0.5m in 1.5s. ( mass of wheel = 3kg, Radius = 0.3m, Radius of gyration = 212mm ). Calculate : a:The linear acceleration of the mass? b: The...
  41. N

    Angular acceleration from change in angular velocity and angle

    Is there a way to calculate angular acceleration from the change in angular velocity and the change in the angle without considering time? How would you accomplish this?
  42. joema

    Angular acceleration given force, moment arm and inertia?

    Homework Statement Find angular acceleration in deg/sec^2 given the following factors: - Total mass: 4889 kg - Moment of inertia: 4620 kg*m^2 - Moment arm length from center of mass: 1.5 meters - Force on moment arm tangent to mass: 1779 Newtons Homework Equations torque = force...
  43. S

    Help needed to convert angular velocity to angular acceleration

    hi, I've calculated ω=5 rad/s How can I calculate angular acceleration (α) I've Mass, M=4Kg Radius, R = 2m and time taken by each single revolution, T=3sec.
  44. R

    Angular Acceleration of a Rigid Bar

    Homework Statement Two identical masses with a mass of m each are connected by a rigid bar of negligible mass and rotate in a vertical plane in an anti-clockwise direction. Homework Equations If the system is released from rest when it is in a horizontal position, determine the...
  45. S

    Calculate angular velocity and angular acceleration of a rotating mass

    I need to calculate the angular velocity of a 2kg mass rotating in a horizontal circle of 2m radius where 1 revolution takes 4 seconds ω=v/r My attempt was this : 4/360=.0111111×57.3=.636rs.
  46. U

    Find the angular acceleration of a hinged beam

    Hi, I have the following problem that I'm lost on. The answer is 41.4 rad/s2 but I don't understand how to arrive at it.Homework Equations ƩT=I(alpha) I=1/3 ML2 for a rod with axis through one end. The Attempt at a Solution I solved the above equations to get (alpha)=T/I, but no matter what...
  47. C

    Inertia and Angular Acceleration

    Homework Statement Two concentric disks are welded together with a small hole through the center. This two disk unit is mounted onto a frictionless horizontal axle through the center hole. Two strings are attached and wound in opposite directions around the outer perimeter of each disk and...
  48. Y

    Torque and Angular Acceleration for a Rigid Body Problem

    Homework Statement A 12.0-kg box resting on a horizontal, frictionless surface is attached to a 5.00-kg weight by a thin, light wire that passes over a frictionless pulley. The pulley has the shape of a uniform solid disk of mass 2.00kg and diameter 0.500m. After the system is released, find...
  49. M

    Archived Find the angular acceleration and velocity at the end of a rod.

    Homework Statement A uniform, straight rod with mass M and length L can rotate about a horizontal axis A in a distance L/4 from the rods end. Vi can disregard friction. Gravity is 9.81 m/s^2. (drawing included at the bottom) 1) Find an expression for the moment of inertia of the rod at point...
  50. N

    Find the Angular Acceleration, acceleration and friction force extered

    Homework Statement The circular disk of 595-mm radius has a mass of 16 kg with centroidal radius of gyration = 500 mm and has a concentric circular groove of 220-mm radius cut into it. A steady force T is applied at an angle θ to a cord wrapped around the groove as shown. If T = 41 N, θ = 39°...
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