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

    Explanation needed in angular acceleration

    Hi all, I am doing some homework from my textbook and I encountered this problem: "Starting from rest, a disk rotates about its central axis with constant angular acceleration. In 5.0 s, it rotates 25 rad. During that time, what are the magnitudes of (a) the angular acceleration and (b) the...
  2. V

    Calculate Angular Acceleration of Cooling Fan | 850 rev/min to Stop

    Question: A cooling fan is turned off when it is running at 850 rev/min. It turns 1500 revolutions before it comes to a stop. A. What is the fan's angular acceleration? B. How long does it take for the fan to come to a stop? I am pretty stumped with this question. I know that I have to...
  3. H

    Constant Angular Acceleration of a wheel

    Starting from rest at t = 0 s, a wheel undergoes a constant angular acceleration. When t = 1.9 s, the angular velocity of the wheel is 6.2 rad/s. The acceleration continues until t = 15 s, when the acceleration abruptly changes to 0 rad/s2. Through what angle does the wheel rotate in the...
  4. T

    Angular Acceleration of a rotating wheel

    A rotating wheel requires 2.98 s to rotate through 37.0 revolutions. Its angular speed at the end of the 2.98 s interval is 98.8 rad/s. What is the constant angular acceleration of the wheel? First I tried acceleration = (98.8rad/s - 0 rad/s) / 2.98 s - 0s = 33.15, which was incorrect...
  5. P

    Angular acceleration of a softball

    One method of pitching a softball is called the "windmill" delivery method, in which the pitcher's arm rotates through approximately 360° in a vertical plane before the 198 gram ball is released at the lowest point of the circular motion. An experienced pitcher can throw a ball with a speed of...
  6. F

    Rubber wheel (angular acceleration)

    A small rubber wheel is used to drive a large pottery wheel, and they are mounted so that their circular edges touch. The small wheel has a radius of 2.0cm and accelerates at the rate of 7.2rad/s^2 and it is in contact with the pottery wheel (radius 25.0cm) without slipping. Calculate: a) the...
  7. M

    Angular acceleration of an axle

    A disk with a radial line painted on it is mounted on an axle perpendicular to it and running through its center. It is initially at rest, with the line at theta 0 = -90°. The disk then undergoes constant angular acceleration. After accelerating for 3.1 s, the reference line has been moved part...
  8. B

    Angular acceleration spin-dry cycle

    Just checking to see fi I did the math right: During the spin-dry cycle of a wash, the motor slows down from 95 rad/s to 30 rad/s while turning the drum through an angle of 402 radians. What is the magnitude of the angular acceleration of the motor? = 1/2(Wo + W)t 402 = 1/2(95 +...
  9. K

    Calculating Angular Velocity and Time in a Frustrating Problem

    This is the last problem that is frustrating me... A wheel, starting from rest, rotates with a constant angular acceleration of 1.20 rad/s2. During a certain 5.00 s interval, it turns through 32.5 rad. (a) How long had the wheel been turning before the start of the 5.00 s interval? (b) What...
  10. T

    Understanding Angular Acceleration and Speed in a Human Centrifuge

    This problem states: A human centrifuge takes 1.0 min to turn through 20 complete revolutions before reaching final speed. They are asking for angular acceleration (a) and angular speed in rpm (b). The answer to a is 40 rev/min^2 The answer to b is 40 rev/min -I'm have the formulas for...
  11. P

    How Do Forces and Angles Affect Angular Acceleration in a Pulley System?

    there are two blocks on a trapizoid one on the top and one on the side with the slope a wire that goes throu a pully connects the two. determin the the acceleration of the two blocks. block one =m1 block two = m2 pully =m with radius r Ufriction =.36 what i have so far is sum of...
  12. F

    Angular acceleration problem - masses on massless rod

    A 3 kg mass and a 4 kg mass are attached to either end of a 3 m long massless rod. If the system is rotated about the center of mass by a force of 7 N acting on the 4 kg mass, (perpendicular to the rod), what will the size of the angular acceleration of the system be? I used angular...
  13. F

    Angular acceleration problem - fishing reel

    A fish takes the bait and pulls on the line with a force of 2.2 N. The fishing reel, which rotates counterclockwise without friction, is a solid cylinder of radius 0.049 m and mass 0.82 kg. What is the angular acceleration of the fishing reel? I used angular acceleration = RT/I, and got...
  14. E

    Calculating Angular Acceleration of a Shaft

    I have a shaft with radius "r" running at a certain RPM. how can i determine the angular acceleration of the shaft. Do i need any other parameters as well? Can i say that the angular acceleration can be (w^2*r), w is the angular velocity, r being the radius. thanks
  15. C

    What is the Initial Angular Acceleration of a Pivoted Rod with Hanging Masses?

    A rod of length 2.4 m is pivoted at its center and masses of 2.3 kg and 3.1 kg are hung from its two ends. Find the initial angular acceleration of the rod when the system is released from a starting position of the rod that is horizontal. The radius of the rod would be r=1/2(2.4).. which is...
  16. J

    What is the relationship between speed and radius for a car to avoid skidding?

    If a certain car, going with speed v, rounds a level curve with a radius R, it is just on the verge of skidding. If its speed is now doubled, the radius of the tightest curve on the same road that it can round without skidding is: Answer is 4R.. but I don't understand why? I know the...
  17. S

    Angular acceleration of a wheel

    A wheel of radius 0.2m is mounted on a frictionless horizontal axis. The rotational inertia of the wheel about the axis is 0.05kg(m^2). A massless cord wrapped around the wheel is attached to a 2kg block that slides horizontally. If a horizontal force of magnitude P=3N is applied to the...
  18. N

    Simple angular acceleration problemhelp

    Two masses (mA= 2 kg, mB= 4 kg) are attached to a (massless) meter stick, at the 0 and 75 cm marks. The system is then hung from a string, so that it stays horizontal. Now, if mass B was removed, and no additional force was supplied, calculate the size of the angular acceleration of the meter...
  19. H

    Angular Acceleration/ Find angle in period - PLEASE help

    Angular Acceleration/ Find angle in period -- PLEASE help! I'm having trouble with part "B" please help. A.)A dentist's drill starts from rest. After 4.95 s of constant angular acceleration, it turns at a rate of 28600 rev/min. Find the drill's angular acceleration. An- swer in units of...
  20. J

    Another Angular Acceleration Problem

    The problem states: when the play button is pressed, a CD accelerates uniformly from rest to 450 rev/min in 3.0 revolutions. If the CD has a radius of 6.0-cm and a mass of 17-g, what is the torque exerted on it? I used the the forumla tau = I * alpha; I = .5(0.017)(0.06)^2 = 3.06E-5; in...
  21. P

    Angular acceleration & cylinder

    M, a solid cylinder (M=1.59 kg, R=0.127 m) pivots on a thin, fixed, frictionless bearing. A string wrapped around the cylinder pulls downward with a force F which equals the weight of a 0.750 kg mass, i.e., F = 7.357 N. Calculate the angular acceleration of the cylinder. I used, I*alpha= mgr...
  22. P

    What Is the Initial Acceleration of End B When the String Is Cut?

    A rod of length 57.0 cm and mass 1.90 kg is suspended by two strings which are 41.0 cm long, one at each end of the rod. The string on side B is cut. Find the magnitude of the initial acceleration of end B. I tried using torque= I* alpha torque= L x f= (.57)(18.62)=10.6 I got from Newton's...
  23. V

    Determine the angular acceleration of the block

    A 6.59 kg block is released from A on a frictionless track, that slopes down until it reaches the floor, then loops in a circle(kinda like the hotwheels loops). Determine the angular acceleration of the block, alpha, about O, the axis of the loop, at the point P, which is located 45 degrees...
  24. B

    Angular acceleration of a skater

    Hi, I need help with the following problem. A skater does a pirouette at the rate of 2.0 rev / second and then stop within 3/4 rev. Assume that the angular decceleration is constant and calculate its magnitude. I tried to compute it but I found -18 rad/s2. BUt the textbook gives -17...
  25. P

    Solve Angular Acceleration Prof's Puzzle: Conservation of Energy

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  26. Reshma

    What is the drum's angular acceleration?

    A drum of radius R rolls down a slope without slipping. Its axis has acceleration 'a' parallel to the slope. What is the drum's angular acceleration? Please help me solve in polar coordinates.
  27. R

    What is the Angular Acceleration of a Free-Rotating Rod at a Specific Angle?

    A uniform rod (mass=2.0 kg, length=.60m) is free to rotate about a frictionless pivot at one end. The rod is released from rests in the horizontal position. What is the magnitude of the angular acceleration of the rod at the instant it is 60 degrees below the horizontal? Please help! I...
  28. F

    Torque and angular acceleration problem

    Hi, I have a problem that I just can't seem to figure out. Here it is: Four masses are arrnaged as shown below. They are connected by rigid, massless rods of lengths 0.75 m and 0.50 m. What torque must be applied to cause an angular acceleration of 0.75 rad/s^2? A--------B l...
  29. M

    Angular Acceleration of a Cyclist's Wheels: 54 Rev in 10.0 s

    A cyclist starts from rest and pedals such that the wheels of his bike have a constant angular acceleration. After 10.0 s, the wheels have made 54 rev. What is the angular acceleration of the wheels? Use units of "rad/s\^{}2". If the radius of the wheel is 36.0 cm, and the wheel rolls without...
  30. M

    Angular Acceleration Problem/ Solid Cylinder

    1) A solid cylinder of mass M = 1.14 kg and radius R = 6.3 cm pivots on a thin, fixed, frictionless bearing (see Figure). A string wrapped around the cylinder pulls downward with a force F = 4.606 N. What is the magnitude of the angular acceleration of the cylinder? Use units of "rad/s\^{}2"...
  31. M

    Angular Acceleration of Solid Cylinder: Mass, Force, Time

    1) A solid cylinder of mass M = 1.14 kg and radius R = 6.3 cm pivots on a thin, fixed, frictionless bearing (see Figure). A string wrapped around the cylinder pulls downward with a force F = 4.606 N. What is the magnitude of the angular acceleration of the cylinder? Use units of "rad/s\^{}2"...
  32. N

    Calculate Angular Acceleration of Rotating Door

    More questions! A rotating door is made from four rectangular glass panes, as shown in the drawing. The mass of each pane is 91 kg. A person pushes on the outer edge of one pane with a force of F = 58 N that is directed perpendicular to the pane. Determine the magnitude of the door's angular...
  33. N

    Average angular acceleration back for more

    Hey again. It's that time of week, and once again I'm stumped. There are three problems, but we'll take them one at a time. The first is as follows: A certain CD has a playing time of 68 minutes. When the music starts, the CD is rotating at an angular speed of 4.8x10^2 revolutions per minute...
  34. N

    Rod + 2 Particle masses = angular acceleration

    PROBLEM: A rigid rod of mass 8.70 kg and length 2.30 m rotates in a vertical (x,y) plane about a frictionless pivot through its center. Particles m1 (mass=4.30 kg) and m2 (mass=2.60 kg) are attached at the ends of the rod. Determine the size of the angular acceleration of the system when the...
  35. P

    Calculating Angular Acceleration for a Solid Cylinder on a Frictionless Bearing

    M, a solid cylinder (M=1.99 kg, R=0.133 m) pivots on a thin, fixed, frictionless bearing. A string wrapped around the cylinder pulls downward with a force of F which equals the weight of a 0.830 kg mass, i.e, F=8.142 N. Calculate the angular acceleration of the cylinder. I tried drawing a...
  36. F

    Finding Angular Acceleration for a Rotating Wheel with a Hanging Mass

    I'm trying to solve this problem, but keep going around and not getting the correct equation. A wheel of radius R, mass M, and moment of inertia I is mounted on a frictionless horizontal axle. A light cord wrapped around the wheel supports a body of mass m. At time t=0, the body is let go...
  37. T

    Angular Acceleration of game show wheel

    A wheel on a game show is given an initial angular speed of 1.22 rad/s. It comes to rest after rotating through 3/4 of a turn. Find the average torque exerted on the wheel given that it is a disk of radius 0.71m and a mass 6.4kg. I'm lost. I don't really know where to begin. I know the...
  38. S

    Angular acceleration and tension

    A block of mass 2.00 kg and a block of mass 6.00 kg are connected by a massless string over a pulley in the shape of a solid disk having a radius of .25 m and mass 10 kg. These blocks are allowed to move on a fixed block-wedge of angle 30 degrees. Friction = .360 for both blocks. Ok I don't...
  39. U

    Angular Acceleration of Rotating Object: $\frac{\pi}{8}$

    If a rotating object starts at rest and completes one rotation in 4s, what is its angular acceleration assuming its angular acceleration is constant? \omega=\frac{2\pi}{t} \omega=\frac{2\pi}{4} \omega=\frac{\pi}{2} \alpha=\frac{\omega}{t} \alpha=\frac{\frac{\pi}{2}}{4}...
  40. U

    Calculating Angular Acceleration in a Pivoted Rod

    rod -- angular acceleration A long uniform rod length L and mass M is pivoted about a horizonal, frictionless pin passing through one end. The rod is released from rest in a vertical position. The instant the rod is horizontal, what is the magnitue of its angular acceleration. It's angular...
  41. U

    Determine the magnitude of the angular acceleration of the discus

    A discus thrower accelerates a discus from rest to a speed of 25 m/s by whirling it though 1.25 rev. Assume the discus moves on the arc of a circle 1m in radius. Determine the magnitude of the angular acceleration of the discus: ω=angular velocity ω=v/r=25m/s / 1m = 25rad/s ω^2=2ad...
  42. R

    Angular acceleration and torque

    I need some help, I've never dealt with a torque problem that uses friction or mechanical energy. This is the problem: Attached to each end of a thin steel rod of length 1.00 m and mass 6.70 kg is a small ball of mass 1.10 kg. The rod is constrained to rotate in a horizontal plane about a...
  43. B

    Angular Acceleration and a grindstone

    HELP! I keep getting a solution that is not part of the choices. Where am I messing up? A grindstone, originally rotating at 126 rad/s undergoes a constant angular acceleration so that it makes 20.0 rev in the first 8.00s. What is the angular acceleration? a) 0.313 rad/s2 b)...
  44. L

    .Finding Angular Acceleration of a Seesaw

    My main goal was the find the angular acceleration of the seesaw. The swing bar of mass is pivoted at a different point, as shown in the figure. Find the magnitude of the angular acceleration of the swing bar. Be sure to use the absolute value function in your answer, since no comparison...
  45. S

    Angular acceleration and linear acceleration

    For a disk in the x-y plane that is rotating about the z-axis which travels through its center of mass, how does the angular acceleration relate to the linear acceleration of a particle on the body? Is the direction and the magnitude both affected? How do we calculate these in vector form? I...
  46. B

    Finding angular acceleration for this prob

    A rotating wheel requires 3.00s to rotate 37.0 revolutions. Its angular velocity at the end of the 3.00-s interval is 98.0rad/s. What is the constant angular acceleration of the wheel? What i did was i used average w=delta(theta)/delta time. Then i used average w=radical(w^2+wo^2) to find...
  47. J

    What is the magnitude of angular acceleration upon release?

    A dumbbell consists of a slender rod of negligible mass and small spheres attached to each end with mass 12-kg and 6-kg respectively. It is pivoted at its center about a fixed horizontal frictionless axle and initially held in place horizontally. The length of the rod is 50 centimeters and...
  48. C

    Angular acceleration of a pulley

    Two pulleys are glued together and placed on a common axis. The total moment of interia for the pulleys is 22.0 kgm^2. The radius of the smaller pulley is 0.170 meters and hanging from it is a mass 5.94 kg. The large pulley has a radius of 0.510 meters and hanging from it is a mass of 8.41 kg...
  49. G

    How Do You Calculate Angular Acceleration from RPMs?

    Can someone walk me through this problem? A power drill reaches 13164 rpm in 1.01 seconds. What is the angular acceleration? The answer listed is 3.791 rad/s2, but I don't know how to get there. So far, I did (13164 rev x 2pi)/60 seconds to get 1378.5 rad/s (which is 'w', right)? but...
  50. P

    Hammer thrower - Angular acceleration

    A hammer thrower accelerates the hammer (mass = 7.3 kg) from rest within four full turns (revolutions) and releases it at a speed of 27.2 m/s. Assuming a uniform rate of increase in angular velocity and a radius of 2.0 m, calculate (a) the angular acceleration, (b) the (linear) tangential...
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