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Questions tagged [rotational-kinematics]

A tag for questions about rotational motion, including angular velocity and angular acceleration.

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Rotational velocity necessary to make apparent weight equal to “real” weight?

I have been trying to find a solution to this, but I never reach same one that my professor provides. The problem is the following: For an object of mass m standing still on the surface of the ...
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Is it possible to find the linear and angular forces?

Suppose an object has both linear an angular motion. Let's consider the object a sphere. What we know: - The angular velocity and acceleration - The linear acceleration of the center of mass. - The ...
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A rod rotating about a pivot

A long, uniform rod of length L and mass M is pivoted about a frictionless, horizontal pin through one end. The rod is nudged from rest in a vertical position as shown in figure. At the instant the ...
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Relationship between radius of Euler Disk and radius of path

Lets say you have a Eulers Disk of radius a which circulates at a circle of radius R with an angle theta from the vertical, what is the minimum possible radius R of the circle in terms of theta and a?...
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Rotational friction coefficient

How to find the rotational friction coefficient? Can it be found using the same procedure used to find the static friction coefficient?
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Is the angular momentum in uniform circular motion zero?

In uniform circular motion the direction of linear velocity changes (although magnitude is constant), so linear velocity is not constant and we know that the formula of angular momentum contains ...
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Problem with Impure Rolling [closed]

Can someone explain what happens in the below situation Looking at it from the planks frame of reference: The cylinder Velocity= 20(-i) Net friction force on cylinder f=2umg(i) (here u=1/2) ...
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Does acceleration of the rim mean just tangential or both tangential and centripetal acceleration?

On my physics homework, the problem specifies that the acceleration of the rim of a flywheel can't exceed 100g. Does this mean that the tangential acceleration only, or the sum of the tangential and ...
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Rotational motion and Circular motion

What is the difference between rotational motion and circular motion? Are they same or they different?
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Point of application of tangential velocity in rotational motion

The tangential velocity of a particle in a rigid body is given by: $\vec{v}=\vec{\omega}\times \vec{r}$. Since the cross product is perpendicular to both $\vec{\omega}$ and $\vec{r}$, the velocity $\...
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Single number to quantify difference between two local reference frames?

I'm working with some satellite data that defines the spacecraft reference frame from two star cameras and two different measurements of orientation configuration of the cameras, and I'm trying to ...
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8answers
446 views

What actually is the vector of angular momentum?

If an object spins around a central point, it gets angular momentum which is a vector with an orientation dependent on whether its clockwise rotation or anticlockwise, i get that. But what the vector ...
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What is wrong with this reasoning?

Suppose a particle is rotating about a point at a distance $r$, then since $r$ is constant $\frac{\text dr}{\text dt}=0$ so the component of velocity along the position vector should be zero. ...
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1answer
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Is there a reference frame in which the static friction from rolling does positive work?

I am worried this will be deleted as a duplicate question, so I will try to be extra clear what I am asking: In some reference frames, static friction can do positive work. If you have a crate in the ...
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Could the source of dark energy be the universe rotating in a higher dimension?

As I understand it, the centrifugal force in a merry-go-round increases as we move further away from the center. Could the universe be spinning in a higher dimension (or even just spinning in a ...
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Can a tilted wheel roll straight?

The common explanation of why a wheel that is falling to one side will turn towards that side to balance itself is gyroscopic precession, i.e. the torque produced by the falling of the wheel plus the ...
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Concept of polarization in microwave rotational spectroscopy

I am trying to understand the concept of polarization of molecules after they are excited by a microwave pulse. The context is: The complexes are produced in a pulsed supersonic jet expansion of a ...
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1answer
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how does a car move? and how do the brakes affect its velocity? [duplicate]

im doing a project that requires me to understand how cars move. from what I understand , its the friction that is creates in the tires that enables the tire to rotate, which then push the car forward....
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2answers
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Impulse on a Gyroscope

I've been studying gyroscopes, and I understand why a fast spinning gyroscope doesn't fall. However, I don't understand why a slow spinning gyroscope does fall, or why a large enough impulse to a fast ...
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1answer
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Rotational Motion (angular momentum)

I don't understand why the angular momentum remains constant even after the distance of the particle (from the origin) keeps on increasing. Maybe I'm not reading the graph the way it is but I don't ...
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1answer
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Velocity of a rotating wheel with axle unlocked from wheel vs locked

For a bike wheel rolling down an incline as like the image, initially the axle of the wheel is not locked to the wheel, so the axle rotates as it moves down the incline but the wheel itself possesses ...
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2answers
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Why is the magnitude of friction acting on the rear wheels greater than the magnitude of friction acting on the front wheels?

When a car is accelerating on a horizontal road , friction acts in the forward direction on the rear wheel and in the backward direction on the front wheel . But I am not able to understand why the ...
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What is centre of rotation and a ref. point fixed wrt to the body?

I'm studying Analytical Mechanics, and in the section about the kinematics of rigid body, it is mentioned the following concepts: Center of rotation a reference position that is fixed with ...
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1answer
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Effect of spin on the deflection of a rigid body

Suppose an x-y coordinate axes is set on the ground, then a spherical object is projected in the forward direction (the positive y direction) and while moving in this forward direction it also ...
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A body is projected from ground with some angle to the horizontal, how the angular momentum about the initial position of the motion increases?

A body is projected from ground with some angle to the horizontal, how the angular momentum about the initial position of the motion increases? I have tried to solve this problem using parallel axis ...
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1answer
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Circular motion of a ball suspended from the rim of a rotating table [closed]

Susppose there is a ball with radius $r$ suspended to the rim of a circular spinning table with radius $R$ by a string with length $l$ which makes an incline angle $\theta$ with the vertical axis. If ...
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1answer
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Billiard ball with side spin

A cue ball is travelling along a snooker table. Initially, it has only side spin (yaw). As it travels it will develop a rolling spin (pitch). Can the ball develop any (roll) and thus move off the ...
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A problem of rotational kinematics/dynamics

The fastest rotational speed for a disc shaped object was achieved in 1985 . The flywheel was spun up to a tip speed of 1405 m/s, at which point it failed, due to the stresses in the materials ...
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1answer
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Angular Momentum and assymetric axis

The question I came across , If a semicircular disc rotates uniformly (const. angular velocity) about an axis passing through its Centre of mass , and prependicular to its plane , do we need an ...
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3answers
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Rotational KE vs Translational KE [closed]

Q. Horizontal electric field E = mg/q exists as shown in the figure and a mass m is attached at the end of a light rod. if mass m is released from the position as shown in the figure. find the angular ...
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1answer
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Rolling on a track in vertical plane

A sphere of mass m and radius r is released from rest at point A on a track in vertical plane. The track is rough enough to support rolling between A and B and from B onwards it is smooth. My ...
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2answers
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Why the faster you spin the highest the pitch get in a whirly tube? [duplicate]

I would like to understand why the faster you spin, higher normal modes are excited This is the tube i'm talking about, i think it's used as a kid's toy: https://www.youtube.com/watch?v=eCOZxzO3FvE ...
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1answer
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Directional cosines and rigid bodies

Suppose $Oxyz$ is fixed in space. We specify one reference point in the rigid body using Cartesian coordinates in $Oxyz$. We use this point as the origin of the body-fixed frame $O'x'y'z'$. Consider ...
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Effect of earth's rotation in ballistics

For this purpose, let's consider earth's rotations constant. Do earth rotation momentum get transfered to any object (a missile for example) that get's lauched? If so, why do we have to consider earth ...
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2answers
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Find the time when tangential acceleration is equal to radial acceleration [closed]

A particle begins to move along a circular path of radius R with a constant magnitude tangential acceleration of $a_t$. After time $t$ it's the centripetal acceleration is equal in magnitude to ...
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1answer
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Rotating Torque

I have started learning about rotating torque from Berkely Physics Course-1. I came across the bead on massless rod setup as shown in the figure below. Since omega and angular momentum are not ...
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1answer
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Addition theorem for angular velocity --> “addition theorem for angles”

I'm wondering if it is possible to go from the addition theorem for angular velocity to the "addition theorem for angles". For example (I used the same notations of Wiki): $${^N\!\omega^B} = {^N\!\...
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Why do office chairs rotate when pushed/pulled out?

A common source of frustration when I'm at work is the fact that my rolling office chair's wheels rotate whenever I push it forward or backward from my desk, which can cause it to bump my computer ...
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Velocity of a satellite with a polar orbit with respect to the surface of the earth

Let's say I'm tryng to derive the expression for the velocity of a really low orbit satellite. Let $S$ be the frame of reference of the earth's center (in rest). Let $S'$ be the frame of an observer ...
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What happens when an impulse is applied at right angles to one end of a rod (free to move on a frictionless surface)? [duplicate]

What will be the difference if we apply this impulse at the center of the rod? Will the translatory motion be same in both the cases?
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Conceptual explanation: Finding revolutions over a given time interval

The following question from NJCTL was assigned for me as homework. It is not a heavy computational problem, but rather, a conceptual one. I reviewed the meta guide regarding these types of questions ...
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3answers
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Why does friction not accelerate a wheel?

It seems like a silly question because this defies common sense, but it appears that friction is supposed to accelerate a wheel (not attached to anything). We can derive from Newton's laws that $\...
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1answer
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Position vector from the axis of rotation in a rotating sphere

In Fluid Mechanics textbook, I found the following example: In the rotating sphere viscometer, a solid sphere of radius $R$ is suspended from a wire and rotates slowly at constant angular ...
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What happens to moment of inertia if a body is divided into 2 congruent part?

If a circular disk is cut in half, and a square plate is divided into 2 identical right angled triangle, when the axis of rotation is not changed i.e if the square plate was rotating about an axis ...
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Does rotational kinetic energy always implies translational kinetic energy?

I always thought that whenever there's rotational kinetic energy, there's also translational (linear) kinetic energy. The opposite is not true. There can be translational kinetic energy without having ...
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Theorem of relative derivatives, Mozzi Equations and Theorem of relative motion

I am currently studying Kinematics in a Mechanics course and I am unable to find sources besides college material to help me studying what I learn in classes, probably due to my ignorance regarding ...
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Boomerang problem, can't figure out the angular acceleration? [closed]

Here is the problem: A boomerang is thrown with an initial linear velocity of 5 m/s at an angle of 30 degrees vertically. The initial angular velocity is $2\frac{revolutions}{s}$At its peak, it has ...
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2answers
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Intuition for formula of tangential component of acceleration in general curvillinear motion

In certain problems of plane motion, the position of the particle P is defined by its polar coordinates $r$ and $\theta$. It is then convenient to resolve the velocity and acceleration of the particle ...