What is Rotational motion: Definition and 610 Discussions

A rotation is a circular movement of an object around a center (or point) of rotation. The geometric plane along which the rotation occurs is called the rotation plane, and the imaginary line extending from the center and perpendicular to the rotation plane is called the rotation axis ( AK-seez). A three-dimensional object can always be rotated about an infinite number of rotation axes.
If the rotation axis passes internally through the body's own center of mass, then the body is said to be autorotating or spinning, and the surface intersection of the axis can be called a pole. A rotation around a completely external axis, e.g. the planet Earth around the Sun, is called revolving or orbiting, typically when it is produced by gravity, and the ends of the rotation axis can be called the orbital poles.

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  1. B

    How to find the coefficient of friction in a rotor-ride?

    Homework Statement I have no values at all, so it's just going to be the variables in the relevant equations. I need to define mu using those variables. A carousel is moving in a circle at velocity v and has a radius r. It is moving fast enough that each person with mass m is pinned against the...
  2. S

    Conceptual angular momentum question

    The question is: A turtle is on a turntable. which is rotating on frictionless bearings at an angular velocity omega. The turtle walks towards the outside of the turntable (away from the center). Which of the following is true about the system's angular velocity omega and its angular momentum...
  3. M

    Rotational motion: Find angular displacement when rotation speed is changing

    Homework Statement A torque acts on a wheel rotating at 19.8 rad/s and increases its angular speed to 23.5 rad/s in 11.2 s. Find the angle through which the wheel turns during this time. Homework Equations omega = theta/time The Attempt at a Solution 23.5 - 19.8/11.2 = .33rad/s/s --- this is...
  4. F

    Prelab rotational motion question

    There is an experimental set up that looks like the attitude file. 1) for mass hanging down the pulley write Newton's second law 2)since the sensor measures α find substitute a with a variable containing α 3) for the drum (horizontal pulley) find another equation for torque other than τ = Iα 4)...
  5. gimak

    Deriving work-kinetic energy theorem for rotational motion

    Homework Statement How to derive W=(.5*I)*((ωf^2)-(ωi^2)) from W=τ*(θ) Homework Equations The two equations seen above (big W is work; little w is rotational velocity, τ is torque, alpha=rotational acceleration). s=r*θ a=r*(alpha) (ωf^2)-(ωo^2)=2*(alpha)*(θ) F=r*τ F=ma...
  6. T

    Why Is Inertia Crucial in Understanding Rotational Motion?

    Why do we use inertia in rotational motion and not the whole mass of an object ?
  7. O

    Rotational motion magnitude question -- Rod mounted on a pivot

    I've attempted this problem several times and keep getting 14 rads as the answer but its not an available answer choice... any help would be greatly appreciated. The problem: A uniform rod (mass = 2.0 kg, length = 0.6 m) is free to rotate about a frictionless pivot at one end. The rod is...
  8. B

    Rotational Motion and Torque: Solving for Angular Acceleration

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  9. H

    Archived Rotational Motion -- a hollow ball rolls down a ramp

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  10. D

    Conservation Laws in Rotational Motion

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  11. D

    Combined linear and rotational motion question

    Homework Statement A small solid disk (r<<R), mass m = 9.3 g, rolls on its edge without skidding on the track shown, which has a circular section with radius R = 9.7 cm. The initial height of the disk above the bottom of the track is h = 30.8 cm. When the ball reaches the top of the circular...
  12. phoenixXL

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  13. A

    Combined translational and rotational motion of a rigid body

    The velocity of any point P of a rigid body in rotation plus translation is \vec{}vp=\vec{}vCOM+\vec{}vp,COM. Now |\vec{}vCOM|=v and \vec{}vp,COM =rω . But v and rω are same thing as v=rω ,so velocity of the particle every time will be √2 v.Then what is the difference between \vec{}vCOM and...
  14. S

    Rotational motion and an incline

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  15. O

    Maximizing Car Efficiency: Utilizing Flywheels for Rotational Motion

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  16. I

    What is the actual definition of rotational motion?

    Ok so I roughly know what rotational motion is (e.g. the spinning of a DVD) but I wish to know the textbook definition for it. I tried Googling it but to no avail. The first link on Google gives this: http://en.wikipedia.org/wiki/Rotation_around_a_fixed_axis But as mentioned above, that...
  17. T

    Separability of vibrational and rotational motion for diatomics

    I'd like some help justifying the approximation that the vibrational and rotational motion of a diatomic molecule is separable. For two atoms of masses m1 and m2 the full hamiltonian is H=-\hbar ^2 /2m_1 \nabla _1 ^2 - \hbar^2 /2m_2 \nabla _2 ^2 + V(r-r_0) Where V(r-r0) is the potential...
  18. R

    Rotational Motion Homework: Mass 12 kg Rod, Pivot Friction-Free

    Homework Statement Consider a uniform rod of mass 12 kg and length 1.0 m. At its end, the rod is attached to a fixed, fricition free pivot. initially the rod is balanced vertically abbove the pivot and begins to fall (from rest) as shown. Determine a) the angual acceleration of the rod as...
  19. C

    Rotational Motion Problem - 16

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  20. C

    Rotational Motion Problem - 15

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  21. C

    Rotational Motion Problem - 14

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  22. C

    Rotational Motion Problem - 13

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  23. C

    Rotational Motion Problem - 12

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  24. C

    Rotational Motion Problem - 11

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  25. C

    Rotational Motion Problem - 10

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  26. C

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  27. C

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  28. C

    How Does Bullet Collision Affect Hoop Velocity in Rotational Motion?

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  29. C

    What is the Solution to a Rotational Motion Problem?

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  30. C

    What is the solution to this rotational motion problem?

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  31. C

    Rotational Motion: Solving a Problem with Translational and Angular Motion

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  32. C

    What is the solution to this Rotational Motion problem?

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  33. C

    Understanding Friction in Rotational Motion: Solving a Common Misconception

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  34. C

    How Can Vector Analysis Improve Understanding of Mechanics Problems?

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  35. S

    How Much Energy is Stored in a Hurricane's Rotation?

    Rotational Motion Question -- please help Homework Statement Estimate the energy stored in the rotational motion of a hurricane. Model the hurricane as a uniform cylinder 300 km and 5 km high, made of air whose mass is 1.3 kg/m^3. Estimate the outer edge of the hurricane to move at a speed...
  36. NATURE.M

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  37. NATURE.M

    Rotational motion: Expression for Angular Velocity

    Homework Statement A solid flywheel of radius R and mass M is mounted on a light shaft of radius r so that the axis of rotation is horizontal. A light, inelastic rope is wound around the drive shaft and is connected, via a light, frictionless pulley to a mass m, which is suspended a height h...
  38. H

    Help with rotational motion work

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  39. N

    Rotational Motion Conceptual Question

    Homework Statement A spool of wire rests on a horizontal surface as in Figure P10.87. As the wire is pulled, the spool does not slip at the contact point P. On separate trials, each one of the forces F1, F2, F3, and F4 is applied to the spool. For each one of these forces, determine the...
  40. P

    How is torque calculated for rotational motion involving a winch system?

    1. Homework Statement This question is about forces and rotational motion. (a) Figure 1.1 illustrates a force of 180 N acting at a perpendicular distance of 0.40 m from a point O. Calculate the torque about O. (b) Figure 1.2 illustrates a circular drum of radius 0.080 m around which a...
  41. M

    Interpreting force in rotational motion

    56. A motor is connected to a solid cylindrical drum with diameter 1.2 m and mass 51 kg. A massless rope is attached to the drum and tied at the other end to a 38-kg weight, so the rope will wind onto the drum as it turns. What torque must the motor apply if the weight is to be lifted with...
  42. T

    Rotational motion of rear wheels

    A 1500 kg car is driven onto a pair of ramps so that it fronts wheels have been raised 0.3 m above the rear wheels. The wheel base of the car is 2.4m and it center of gravity is located at the midpoint between the front and rear wheels. How much of the car's weight is supported by the rear...
  43. 0

    Work–kinetic energy theorem for rotational motion. need to be symetri?

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  44. N

    A simple rotational motion question

    Homework Statement A solid cylinder of mass M =1kg and radius 0.5m is pivoted at its centre and has three particles of mass m=0.1 mounted at its perimeter on the curved surface.The system is initially at rest.Find the angular speed of the cylinder,when it is swung through 900 in anticlockwise...
  45. PsychonautQQ

    Rotational Motion / Torque problem (what did i do wrong?)

    Homework Statement A thin, light wire is wrapped around the rim of a wheel,. The wheel rotates without friction about a stationary horizontal axis that passes through the center of the wheel. The wheel is a uniform disk with radius R = .280m. An object of mass m=4.2kg is suspended from the...
  46. P

    How Does Friction Affect Energy Conservation in Rotational Motion Experiments?

    Homework Statement We performed a small experiment in class which had us attach a mass to a string which hung on a pulley which led to a rotating object. We were then told to write down a conservation of energy equation stating that the initial energy is equal to the final energy. We were...
  47. Y

    Rotational Motion Question with Work Energy Theorem

    Homework Statement A 392-N wheel comes off a moving truck and rolls without slipping along a highway. At the bottom of a hill, it is rotating at 25.0rad/s. The radius of the wheel is .6m and its moment of inertia about its rotation axis is 0.800MR2. Friction does work on the wheel as it...
  48. L

    Rotational motion problems involving radians

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  49. S

    Rotational Motion of a toy airplane

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  50. N

    Rotational motion on pulley system

    Homework Statement A string passing over a pulley has a 3.80-kg mass hanging from one end and a 3.15-kg mass hanging from the other end. The pulley is a uniform solid cylinder of radius 4.0 cm and mass 0.80 kg. If the bearings of they pulley were frictionless, what would be the acceleration...
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