Rotational motion Definition and 614 Threads

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. BobG

    Kinetic Energy due to rotational motion

    The kinetic energy of a body due to rotational motion is a scalar using the following equation: E=\frac{1}{2}I\omega^2 Except, the moment of inertia is nomally expressed as a matrix and the angular velocity as a vector, as in the equation for angular momentum: \vec{H}=[I]\vec{\omega}...
  2. S

    Rotational Motion FInding the total ENergy

    Particulars: ball has a radius of 2.5 cm a mass of .125 and is rolling across a table with a speed of .547 m/s, this table is 1.04 m off the ground. It rolls to the edge and down a ramp How fast will it be rolling across the floor? First I found the Gravitational Potential Energy: Ep=mgh...
  3. E

    Solving a Rotational Motion Problem: Determining Angular Velocity & Speed

    Hello, I need to confirm my solution to this problem: A thin rod of length l stands vertically on a table. The rod begins to fall, but its lower end does not slide. (a) Determine the angular velocity of the rod as a function of the angle \phi it makes with the tabletop. (b) What is the speed...
  4. R

    Rotational motion of a car's tires

    A car accelerates uniformly from rest and reaches a speed of 19.0 m/s in 7.00 s. The diameter of a tire is 64.0 cm. (a) Find the number of revolutions the tire makes during this motion, assuming no slipping. (b) What is the final rotational speed of a tire in revolutions per second...
  5. N

    Rotational Motion: Can 1 Force Make It?

    It is possible for a free body to make rotational motion with the effect of one only force?
  6. P

    Can you help check my answers for rotational motion homework?

    I was just wondering if anyone has a few minutes if they could check my answers for my homework. I have 7 questions on Rotaional Motion 1)A potter's wheel moves from rest to an angular speed of .20rev/s in 30s. Assuming constant angular acceleration, what is its angular acceleration in...
  7. M

    Rod Rotational Motion Question

    I think I have asked this question before, but I either forgot the answer, or never got one. A uniform rod is floating in otherwise empty space and a force is exerted on one end of the rod. What will be the acceleration of the rod's rotation and translation? Where will the center of rotation be?
  8. M

    Rotational Motion Clarification

    I got a little confused thinking about this. Consider a ball attatched to a (massless) rod. This system is to be accelerate about the free end of the rod. From what I know, the moment of inertia for this system would simply be the mr^2, since this is the same case as a free ball being...
  9. S

    2 Super Hard Rotational Motion Problems

    1.) A car rounds a banked curve where the radius of curvature for the road is R, the banking angle is 0(theta), and the coefficient of static friction is [mu]. (a) Determine the range of speeds the car can have without slipping up or down the road. (b) What is the range of speeds possible if R =...
  10. A

    Understanding of rotational motion

    Hello anyone that can help. I am trying to gain an understanding of rotational motion, including (tangential speed, angular momentum, centripetal force and so on). The first question I was hoping that someone could help me is: An automobile speedometer is configured yo read speed proportional...
  11. M

    Rotational Motion: Force on Rod, Translation vs Rotation

    Imagine a rod in space. If I exert a force at one end, will the rod translate, rotate, or both? How do I determine what it will do?
  12. C

    Does Spinning Affect Floating in a Rotating Room?

    Okay guys, I have a serious question. In our Physics class, we were discussing rotational motion. Someone asked the question "If we were falling in a room (we're floating) and someone started to spin the room, would we still be floating? Or would we hit the walls?" If anyone could help me with...
  13. T

    Rotational motion of a washing machine

    Hi everyone….well I have just started to learn about rotational motion, therefore, I am really confused so I have two different problems that I need help on. 1.) Q: A washing machine goes into the “spin cycle”. From rest the washer starts rotating, gaining 1 rev/sec of rotational velocity...
  14. D

    Seriously stumped by rotational motion

    Here's the problem I'm stuck on: An 8 lb. block slides on a horizontal table; between the block and table, coeffecient of friction = 0.25. The block is pulled by a string over a light, frictionless pulley wrapped around a solid cylinder of radius 2 ft. and weight 8 lb. The cylinder is...
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