Rotational Definition and 1000 Threads

A simple rotating system with no external forces acting on it carries a fixed angular momentum and an associated rotational kinetic energy. If the system changes its internal configuration, such as a spinning skater retracting or extending his/her arms, the angular momentum remains constant...

Some background information: I'm doing some reading up for PhO (so it's beyond what I'm supposed to learn), and so I'll post all my questions here (regarding both concepts and actual practice questions). Sorry if you feel there is a lack of effort on my part, but sometimes I'm really lost and...

Homework Statement A small sphere of radius r0 = 1.4 cm rolls without slipping on the track shown in the figure whose radius is R0 = 40.0 cm. The sphere starts rolling at a height R0 above the bottom of the track. Assume that it leaves the track after passing through an angle of 135° as...

Can you do "sum of all moments" on a point that's not a rotational axis? For instance, in this structure, with the two wires holding the beam http://img228.imageshack.us/img228/3687/twowiresj.jpg Can I do sum of all moments on B? Or is it not allowed because it's not a pivot point?

Homework Statement A 600 kg car is going around a banked curve with a radius of 110m at a speed of 24.5 m/s. What is the appropriate banking angle so that the car stays on its path without the assistance of friction? Homework Equations N cos{theta} = mg N sin{theta} = mv^2/r The...

First of all, hi! I'm new here. Homework Statement Rather than a specific problem, my friend and I are doing an Extended Experimental Investigation on the energy transfer of dominoes for our grade 12 assignment. 2. The attempt at a solution We have approached it using loss of gravitational...

Homework Statement A block of mass m1 = 2.00 kg and a block of mass m 2 = 6.00 kg are connected by a massless string over a pulley in the shape of a disk having radius R = 0.250 m and mass M = 10.0 kg. These blocks are allowed to move on a fixed block – wedge of angle 30.0°, as shown in...

Homework Statement Two 2.1 kg balls are attached to the ends of a thin rod of negligible mass, 63 cm in length. The rod is free to rotate in a vertical plane about a horizontal axis through its center. With the rod initially horizontal as shown, a 50 gm wad of wet putty drops onto one of the...

Hi! I'm wondering what the effects of a variable mass of elementary particles on the rotational and vibrational energy-transitions would be like? Would they increase, decrease or stay the same? Thank you for your help! Regards

Homework Statement A ball attached to a string starts at rest and undergoes a constant angular acceleration as it travels in a horizontal circle of radius 0.30 m. After 0.65 sec, the angular speed of the ball is 9.7 rad/s. Determine the magnitudes of the ball’s tangential, centripetal, and...

Simple question: Is there a reason behind the right hand grip rule, or is it just like that (inexplicable)? How do we know that for an object with counter-clockwise rotation (e.g. on the table), the angular velocity is upwards?

They're both this? http://img37.imageshack.us/img37/4795/acccelerationrotational.jpg

I took physics in school, but our class kind of skipped over rotational motion, so I was just reading about it myself. I was wondering about whether rotating an object absorbed some of the energy put into it and, if so, how to calculate how much is transferred to the rotation.

Homework Statement I'm not using numbers because I only want to understand the mathematical relationship. This is not a coursework question, but I imagine it stems from coursework level physics. I am trying to design a rotating arm for my own use and I want to calculate bracing requirements...

Im looking over an example that was given in class that I jotted down in my notes; the question posed was...A 320 kg motorcycle includes two wheels each of which is 52 cm in diameter and has rotational inertia 2.1 kg*m^2. The cycle and its 75 kg rider are coasting at 85km/hr on a flat road when...

Homework Statement A disk of radius r meters has a string wrapped around its perimeter. A mass of m kilograms is attached to the end of the string and is allowed to descend freely from a height of h meters, it takes t seconds for the mass to travel the distance. Find the moment of inertia (I)...

This a question that has been haunting me for some time now. Regarding the rotational motion of rigid bodies why wasn't the moment of inertia defined as the integral sum elements of infinitesimal mass time the radius from the axis of rotation rather than the radius squared. In this case the...

Homework Statement A solid rectangle of uniform density has one corner at the origin. It has a mass of 50 kg. The rectangle has a length of 4 m in the z-direction, a length of 3 m in the y-direction, and a length of 2 m in the x-direction. The pivot is at the center of mass. There is a 50 N...

How do i convert spring energy to rotational energy? I am building a 'green device' that allows a bicycle to move forward using stored energy (compressed spring energy). So i am figuring out how do i change the spring energy stored to rotational energy so that th bike will be able to propel...

I'm looking for a crank that can give me linear movement to rotation (not the other way around). There is a component that I'm aware of called a uni-directional drive that turns rotation movement in either direction into movement in only on direction... stick a rack in the mix and there is...

Homework Statement The moment of inertia of a fly wheel about it's axis is 20 kg m2. A constant torque of 40 N m is applied to the initially stationary fly wheel. Find it's rotational KE after 3 seconds assuming there is no friction in the system? Homework Equations...

Im studying for a final, there are a few questions about rotational motion that i have, can anyone please help? A 5.2 kg disk of radius 2.3 m initially rotates about its axis at 6.4 rad/s. A tangential 7.4-N frictional force is applied to the rim of the disk. How many revolutions does the...

In uniform linear motion, an object moves at a constant speed v0. And as long as no acceleration is applied onto the object, it will continue move at the same speed and direction forever. For uniform circular motion to happen, an object must move at a constant speed v0 with a constant...

How does friction affect the rotational inertia and angular velocity of a hollow cylinder rolling down an inclined plane? Assuming the cylinder isn't slipping

Homework Statement A NASA astronaut is placed in a rotating machine to see how well their bodies withstand G Force. What rotational speed is needed in a device that has a 6.25 m radius to allow a 75.8 kg astronaut to experience a force that is twice his normal weight (or 2g)?Homework Equations...

Homework Statement Two masses are suspended from a pulley system. The pulley itself has a mass of .2kg, a radius of .015m, and a constant torque of .35Nm due to friction between the rotating pulley and its axle. What is the magnitude of acceleration of the suspended masses if m1=.4kg and m2 =...

Homework Statement A sheet of material, mass 2kg, uniform density, is in the shape of a right triangle bounded by the lines y=0, x=0, and y=4-x. Its attached to the origin, and free to rotate about the y axis. A force of 1000 Newtons is applied perpendicular to the plane, located at the x=4...

Homework Statement A uniform, solid cylinder with mass M and radius 2R rests on a horizontal tabletop. A string is attached by a yoke to a frictionless axle through the center of the cylinder so that the cylinder can rotate about the axle. The string runs over a disk-shaped pulley with mass M...

Homework Statement A 20kg solid disk (I=1/2Mr^2) rolls on a horizontal surface at the rate of 4.0m/s Calculate its total kinetic energy The Attempt at a Solution I think that simply equating the KE to (0.5)(m)(v^2) would be a wrong solution because then I would not use the moment of...

Homework Statement A wheel starting from rest accelerates at 1.2 rad/s² counterclockwise. A) How long does it take to turn through 60 revolutions? B)What is the rotational speed at that time? 2. The attempt at a solution I converted 1.2rad/s² to 1.885 rev/s² by dividing by 2πrad (2...

Block 1 has mass m1 = 460g, block 2 has mass m2 = 500g, and the pulley, which is mounted on a horizontal axle with negligible friction, has radius R = 5.00cm. When released from rest, block 2 falls 75.0 cm in 5.00 s without the cord slipping on the pulley. (a) What is the magnitude of the...

Homework Statement http://i.imgur.com/2Pi18.png Homework Equations The Attempt at a Solution Sorry to say this, but I am completely clueless about these questions. I don't know how to start what to consider. Would anyone like to help me? Thanks!

Hi, I was wondering if the formula for rotational energy: E = 1/2 * L * w where L is the angular momentum and w is the angular velocity, is actually correct for relativistic velocities. Using L = p * r and w = v / r where p = the linear momentum = m * v We get...

Homework Statement http://apcentral.collegeboard.com/apc/public/repository/ap04_frq_physics_cm_36191.pdf The problem can be found here. I am stuck on problem 2 d. Homework Equations I = m(g-a)R2 / a //found in part c The Attempt at a Solution I don't understand why the...

Homework Statement A solid disk of mass 10 kg and radius 1 m is spinning around its central axis at a rate of ω = 20 rad/s. A force of magnitude 5 N is applied to the disk. Recall that the moment of inertia of a solid disk is I=(1/2)mr^2 . (a) Draw the disk and indicate the direction of...

In an inertia experiment using equipment very similar to the link below, I determined the following: Trial with two 100 g masses near the ends of the rotating apparatus (larger moment arm): - Final translational kinetic energy: 5.73 * 10^(-4) J - Final rotational kinetic energy: 0.638 J...

Homework Statement A solid sphere with a mass 8.2kg and radius 10cm is sliding along a frictionless surface with a speed 5.4m/s while at the same time spinning. The sphere has 0.31 of its total kinetic energy in translational motion. How fast is the sphere spinning? Homework Equations...

Hi I am analysing some piping which starts off as being aligned with the global axis system (X Y Z). So axially its X, laterally is Y and Z is vertically upwards. Due to bends etc. the end of the pipe is in a different orientation though still in the same plane - now the local axis system is x...

can a body moving in a straight line be in rotational motion as well?

Homework Statement Can someone help me those 2 questions Homework Equations I don't understand how to convert to angular acceleration The Attempt at a Solution I attempted of finding the torque due to gravity then divided it by the radius for the second question, I got it wrong...

A small, solid, uniform ball is to be shot up from point P so it rolls smoothly along a horizontal path, up along a ramp, and onto a plateau. Then it leaves the plateau horizontally to land on a game board, at a horizontal distance (d=6cm) from the right edge of the plateau. The vertical...

The Problem: A thin rod of mass 0.490 kg and length 1.16 m is at rest, hanging vertically from a strong, fixed hinge at its top end. Suddenly, a horizontal impulsive force (12.7) N is applied to it. a) Suppose the force acts at the bottom end of the rod. Find the acceleration of its center...

Homework Statement There is a system consisting of two masses, m1=20 kg, m2=30kg on a pulley and m2 is 2 meters above the ground, while m1 is on the ground. This is the question: the system released from rest a 30 kg block that is 2m above a ledge. The pulley is a disk with radius of 10 cm...

In Figure, block 1 has mass m1 = 430 g, block 2 has mass m2 = 540 g, and the pulley is on a frictionless horizontal axle and has radius R = 5.3 cm. When released from rest, block 2 falls 80 cm in 5.3 s (without the cord slipping on the pulley). What is the pulley's rotational inertia? Caution...

Listed below are just a things I cannot figure out involving rotational motion (one involves a situation). -Why does Kinetic Friction do no work if bodies roll without slipping? I thought it would add torque to provide more energy for rotational motion. Situation: A solid bowling ball...

Homework Statement A uniform solid sphere rolls on a horizontal surface at 20m.s^-1 and then rolls up an incline which has an angle on inclination of 30°. Ignoring friction, calculate the height attained by the sphere. Homework Equations Weren't given any specific equations to work...

Say you have a convex 2D polygon with a set of vertices rotating on a flat surface. Given the coefficient of friction and the coordinates of each vertex, how can you determine the torque from friction on this polygon? I'm looking more for an algorithm than some big equation, as this is something...

Homework Statement Two blocks A and B are attached to a spring of force constant K and are placed on a horizontal surface. The coefficient of friction between block A and surface is zero while between block B and surface is μ. A spherical ball of mass M, radius R impinges on block A with...

Hi guys, I need to model a ball rolling on an incline plane, and i would like to be able to calculate acceleration due to gravity for a given angle. Currently i have: a = f / m f = m*g*sin(angle) a = g*sin(angle) I am aware this does not take rotational motion into account, which is what...

Homework Statement The four particles shown below are connected by rigid rods of negligible mass where y1 = 6.60 m. The origin is at the center of the rectangle. The system rotates in the xy plane about the z axis with an angular speed of 5.40 rad/s...