# What is Angular kinematics: Definition and 20 Discussions

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. ### I Origin of Centripetal force when the net force toward the center is 0?

to clarify , my purpose isn't to find a solution to my home work , I already did the home work and my thread is more a request of justification or at least a clarification of the forces at play. I need explanation on the general topic not the solution to my question, I am mentioning the question...
2. ### Relating Linear and Angular Kinematics

a) We use the definition of linear speed in terms of angular speed: v = r*omega omega_f = v/r = (1.25 m/s)/(0.025 m) = 50 rad/s omega_0 = v/r = (1.25 m/s)/(0.025 m) = 21.55 rad/s b) We use the definition of linear speed: v = d/t d = vt = (1.25m/s)(74 min)(60 s/1 min) = 5.55 km c) We use the...
3. ### Curvilinear Dynamics and forces

Homework Statement A wedge with face inclined at an angle θ to the horizontal is fixed to a rotating turntable. A block of mass m rests on the inclined plane and the coefficient of static friction between the block and the wedge is µ. The block is to remain at position R from the centre of...
4. ### Unlocking Realistic Rotational Collisions with Physics & Graphics Engines

Hi all! I'm currently working on a graphics/physics engine. The following Wikipedia page was extremely helpful in making rectilinear collisions look natural: https://en.wikipedia.org/wiki/Elastic_collision#Two-dimensional Specifically, the very general vector form of the equation on the bottom...
5. ### Pulling a puck through the hole

Homework Statement Its a classic problem about a puck that is rotating on a frictionless tabble with a velocity v1 and radius r1. It is is connected to a string which runs through a hole a the centre of the table. The string is pulled from below until the radius decreases to r2. Find the work...
6. ### Calculate angular velocity of a ball rolling down incline?

Homework Statement An 7.80-cm-diameter, 400 g solid sphere is released from rest at the top of a 1.70-m-long, 20.0 degree incline. It rolls, without slipping, to the bottom Homework Equations I=2/5 Mr^2 K = 1/2 m*v^2 Kroll = 1/2 Iw2 mgh=K+Kroll The Attempt at a Solution Using the above energy...
7. ### Masses over a Pulley (w/ angular kinematics)

Homework Statement http://imgur.com/koz4PpI Homework EquationsThe Attempt at a Solution I was able to calculate the net torque on the pulley as 55.88 and the Inertia as .352. Those could be wrong, but that's as far as I could get. I really have no idea. Any kind of help/explanation would be...
8. ### How Does a Time-Varying Force Affect Angular Momentum in a Dual-Radius Spool?

Homework Statement a spool of radius R1 and R2 (R2>R1) is kept on hortizontal surface. A force f= 2t N (where t is time ) acts on the inner radius tagentially find the angular momentum of the system about the bottomost point of the spool. Homework Equations v=u+at W=Wi+alpha(t) L=IW+mvrThe...
9. ### Find Angular Velocity when given Angular Acceleration?

Homework Statement Starting from rest, a spinning compact disk undergoes an angular acceleration of 5.0 rad/s^2. What is the angular speed of the disk after 3 revolutions? Homework Equations a=Δω/Δt ω=Δθ/Δt The Attempt at a Solution I do not understand how to solve this equation when I am not...
10. ### Minimum Speed for Balsa Cube Tipping Problem

A solid balsa cube of side length L = 16.0” and mass M = 8.60 kg is at rest on a horizontal table top. It is constrained to rotate about a fixed and frictionless axis, AB, along one edge of the cube. A bullet of mass m = 50.0 g is fired with speed v at the other side of the cube, at height a =...
11. ### Angular kinematics: determining satellite orbital radius

So, I'm working on my semester finals for my high school physics class, and I've run across a problem that has me stumped. I've included the pertinent material below. Homework Statement A rocket with a mass of 2kg and traveling at 14,008.34 meters/second loses 10% of its velocity as finishes...
12. ### Angular Kinematics: Calculating Car's Angular Acceleration

Question The wheel of a car has radius 0.2m and initially rotates at 120 rpm. In the next minute it makes 90 revolutions What is the cars angular acceleration?Attempt So I tried to get the final angular velocity and couldn't and have tried multiple times with the angular kinematics equations...
13. ### Questioning a Linear & Angular Kinematics Equation

Homework Statement I'm reviewing a chapter relating linear and angular kinematics, and I came across this equation.. why does it work and where does it come from? I can't seem to find anything in the textbook explaining it. Homework Equations a = sqrt( (tangential acceleration)2 +...
14. ### Solving Angular Kinematics: Swing Bridge Turned in 120 secs

A swing bridge has to be turned through a right angle in 120 seconds. The first 50.4 seconds is a period of uniform angular acceleration ; the subsequent 34.8 seconds is a period of uniform angular velocity and the third period of 34.8 seconds is a period of uniform angular retardation. Input...
15. ### Angular Kinematics & Moment of Inertia: IforPointM

Homework Statement Four point masses are arranged on the xy plane as follows. Mass1 = 27.0 grams at x = 2.00 cm and y = 2.00 cm. Mass2 = 31.0 grams at x = 0.00 cm and y = 4.00 cm. Mass3 = 49.0 grams at x = -3.00 cm and y = -3.00 cm. Mass4 = 31.0 grams at x = -1.00 cm and y = 2.00...
16. ### How Do You Calculate Angular Acceleration and Speed from a Position Function?

Homework Statement The angular position of a point on the rim of a 18.7 cm rotating wheel is given by θ(t) = 4.7 t2 − 7.2 t +9.7, where θ is measured in radians and t is measured in seconds. What is the instantaneous angular acceleration α of the point at time t = 6 s? What is the...
17. ### How Does Angular Acceleration Affect Spacecraft and Clock Movements?

The moon orbits Earth in 27.3 days. suppose a spacecraft leaves the moon and follows the same orbit as the moon. if the spacecraft has a constant angular acceleration of 1.0 X 10^ -10 rad/s 62 what is its angular speed after 12h of flight? (Hint: At take off the spaceship has the same...
18. ### Angular Kinematics: Calculating Wheel Rotation in 5s

A wheel rotates about a fixed axis. Initial angular velocity of 20 rad/s. During a 5 s interval the ang. velocity increases to 40 rad/s. (const angular acceleration) How many radians does the wheel turn in 5 s? Having a bit of trouble, not quite sure why... so I start out with w = w0 + at...
19. ### What'd I do wrong? [Angular Kinematics]

The problem is: "Pilots can be tested for the stresses of flying high-speed jets in a whirling "human centrifuge" which takes 1.0 min to turn through 20 complete revolutions before reaching its final speed. (a) What was its angular acceleration (assume constant), and (b) what was its final...
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### Relating linear and angular kinematics

im really having a hard tym doing this assignment of mine, i hope someone cud help me out on this one. at t= 3.00s a point on the rim of a 0.200-m-radius wheel has a tangential speed of 50.0 m/s as the whell slows down with a tangential acceleration of constant magnitude 10.0 m/s2...