Rotational kinematics Definition and 130 Threads

Angular displacement is defined as the angle between initial and final radius vector of some arbitrary point on an object undergoing rotation. I’ve seen that some problems include angular displacement bigger than 2 ##\pi## radians. Also, I would note this example: Let us start with definition...

In the solution, the term Lcm and Icm is used. Explain the meaning of these terms? I think cm stands for centre of mass. why that is used in the subscript?does the term angular momentum from the centre of mass of the sphere makes sense? Is the term Lcm and Icm stand for angular momentum of the...

My line of thinking is as follows: \omega_{PQ} = \frac{v_{\perp}}{\ell} = \frac v\ell \frac{\sqrt3}{2} Similarly for rod ##QR## \omega_{QR} = \frac{v_{\perp}}{\ell} = \frac v\ell \frac{\sqrt3}{2} Is my reasoning correct?

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I apologize in advance for any errors in my concepts or assumptions. Feel free to correct me wherever I am wrong. Thanks in advance for the help. There is a vertical shaft which will be operated at around 600 rpm (N) which can be achieved in 2 seconds (or even 4 just an assumption). The shaft...

I was first wondering wether we can solve this question by applying conservation or energy or not but after googling it I found that we can't apply conservation of energy since there will be some energy lost in this case. I don't know how this energy is getting lost. My second doubt was if we...

First we let the static friction coefficient of a solid cylinder (rigid) be ##\mu_s## (large) and the cylinder roll down the incline (rigid) without slipping as shown below, where f is the friction force: In this case, ##mg\sin(\theta)## is less than ##F_{max}##, where ##F_{CM,max}## is the...

Hello, Here in this thread I will derive formulas for relation between two wheels, either teethed (e.g. gears) or non-teethed. In wheel relationship, we have three cases: Two wheels at the same axle Two wheels intersected in parallel (meshed) Two wheels connected by a belt We will examine...

A potter's wheel with a 35.9 cm radius rotates with a 2.91 rad/s2 angular acceleration. After 5.37 s, the wheel has rotated through an angle of 77.7 rad. a)What linear distance did a point on the outer edge travel during the 5.37 s? b)What was the initial angular velocity of the wheel? c)What...

torque=Force*radius*sin(theta) center of mass x direction = ( 0(6 x 10^9 kg)+ (118m)(6 x 10^9 kg)+ (236m)(6 x 10^9 kg) )/(3(6 x 10^9 kg)) = 118m center of mass y direction = ( 0(6 x 10^9 kg)+ (140m)(6 x 10^9 kg)+ (0)(6 x 10^9 kg) )/(3(6 x 10^9 kg)) = 46.7 m radius = (118^2 + 46.7^2)^(1/2) =...

moment of inertia = (1/3) (2.1kg) (1.2m)^2 = 1.0 kgm^2 center of mass= (0.6i, 0j) magnitude of the gravitational torque=9.8m/s^2*2.1kg*0.6m= 12.34N*m position of the new center of mass now : x direction = cos(20)*0.6m=0.56m y direction= -sin(20) * 0.6m = -0.2m change in gravitational...

Homework Statement 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 a displacement about the z axis of 2 meters and about the x-axis of 10 meters. The force applied...

Homework Statement You buy a bottle of water in the store and place it on the conveyor belt with the longitudinal axis perpendicular to the direction of movement of the belt. Initially, both the belt and the bottle are at rest. We can approach the bottle as one cylinder with radius ##R##, mass...

Homework Statement A disk is initially at rest. A penny is placed on it at a distance of 1.4 m from the rotation axis. At time t=0s, the disk begins to rotate with a constant angular acceleration of 1.9 rad/s^2 around a fixed, vertical axis through it's center and perpendicular to it's plane...

Homework Statement .A cylinder P of radius rP is being rotated at a constant angular velocity ωP along positive y-axis with the help of a motor about its axis that is fixed. Another cylinder Q of radius rQ free to rotate about its axis that is also fixed is touched with and pressed on P making...

Angular velocity is the rate of angular displacement about an axis. Its direction is determined by right hand rule. According to right hand rule, if you hold the axis with your right hand and rotate the fingers in the direction of motion of the rotating body then thumb will point the direction...

Homework Statement A uniform cylinder of mass ##M## and radius ##R## is released from rest on a rough inclined surface of inclined surface of inclination ##\theta## with the horizontal as shown in the figure. As the cylinder rolls down the inclined surface, what is the maximum elongation in...

Homework Statement I am referring to this thread and question: https://www.physicsforums.com/threads/rotation-of-a-spool-about-rough-ground.295666/ Here is the problem, restated: Homework Equations ##\tau_{net} = I\alpha## ##\tau = Frsin(\theta)## ##F_{net} = Ma_{cm}## ##\alpha = a_{cm} /...

Homework Statement A wheel rotates with a constant angular acceleration of π rad/s^2. During a certain time interval its angular displacement is π rad. At the end of the interval its angular velocity is 2π rad/s. What is its angular velocity at the beginning of the time interval? Homework...

Homework Statement A small spherical rock of mass collides in space with a large spherical rock of mass as indicated in the diagram. After the collision the rocks stick together to form a single spherical object. https://postimg.org/image/fltmg3bj5/ (New here so I've no clue how to upload...

Homework Statement A small pine tree has a mass of 15kg. Its center of mass is located at .72m from the ground. Its trunk is sawed through at ground level, causing the tree to fall, with the severed trunk acting as the pivot point. At the instant the falling tree makes a 17° angle with the...

Homework Statement In a playground there is a small merry-go-round of radius 1.20 m and mass 220 kg. The radius of gyration is 91.0 cm. A child of mass 44.0 kg runs at a speed of 3.00 m/s tangent to the rim of the merry-go-round when it is at rest and then jumps on. Neglect friction between the...

Homework Statement A wheel of diameter 45.0 cm starts from rest and rotates with a constant angular acceleration of 2.50 rad/s2 . At the instant the wheel has completed its second revolution, compute the radial acceleration of a point on the rim in two ways. 1 Using the relationship...

[Note: Post moved to homework forum by mentor] So I stumbled upon a reviewer for my physics exam tomorrow and I was wondering how the equation was formulated. Your help is very much appreciated :) ! Normally I would consult my professor for this but it's Sunday in my country today so I can't...

Here is the problem I am working on. I have found answers for all of them except part (f), which is the one I need help with. I will report the answers I have so far: A classic 1957 Chevrolet Corvette of mass 1240 kg starts from rest and speeds up with a constant tangential acceleration of 2.00...

Homework Statement A computer disk drive is turned on starting from rest and has constant angular acceleration. If it took 0.680s for the drive to make its second complete revolution, how long did it take to make the first complete revolution? (t=?) Homework Equations Θ=(ct^2)/2 (i think) The...

A very small coin is at distance 10.5 cm from the spindle of a turntable. The turntable starts spinning from rest with constant angular acceleration. In 0.133 s the coin's centripetal acceleration is 1.39 times its tangential acceleration. 1)Find the turntable's angular acceleration. 2)Find the...

Homework Statement A girl and a boy are sitting in a see saw. The girl is 36 kg and sitting 5 m from the fulcrum. The boy is sitting 3 m from the fulcrum. Calculate the mass of the boy and the force on the fulcrum. Homework Equations Fr1=Fr2 The Attempt at a Solution I solved for the boys...

Homework Statement A wheel of radius R starts from rest and accelerates with a constant angular acceleration α about a fixed axis. At what time t will the centripetal and tangential acceleration of a point on the rim have the same magnitude? Homework Equations acp=r x ω2 at= r x α ω= 2π / T...

Homework Statement A bicycle wheel is mounted as in the lab and as shown to the right. This wheel has a mass of 6.55 kg, a radius of R = 38.0 cm and is in the shape of a ring. A mass M = 1.85 kg is attached to the end of a string which is wrapped around an inner hub which has a radius r = 5.40...

Homework Statement This isn't so much of a problem as a general question. I am trying to find the starting velocity of a spinning ball going upwards (in air, close to Earth's surface, only force acting on it is the gravitational force) until its linear velocity reaches zero. I found the initial...

Good afternoon! I've been mulling over this question for a bit and I can't seem to understand what it is asking. This is a question for an introductory calculus-based physics university course. 1. The Problem: A uniform disk, such as a record turntable, turns 8.0 rev/s around a frictionless...

Homework Statement A phonograph turntable with an initial angular velocity of 78 rpm continues turning for 40 rotations after being switched off. What is the angular deceleration of the turntable? Assume constant angular deceleration. Homework Equations \alpha=(\omega-\omega0)/t...

Homework Statement A turntable is a uniform disc of mass m and radius R. The turntable is initially spinning clockwise when looked down on from above at a constant frequency f_0. The motor is turned off at t=0 and the turntable slows to a stop in time t with constant angular deceleration...

Homework Statement Consider a system of two masses joined by a massless string with the string passing over a massless frictionless pulley with a radius of 5.0 cm. The mass of the left is 9.00 kg and the mass on the right is 1.60 kg. Find the angular acceleration of the pulley when the...

1. Problem statement 2. Related equations I = bmr^2 Energy equations (linear and rotational) 3. Attempt Part a) I know that the distance or height traveled by the box is [h - d] because center of the mass of box is just d. Initial kinetic energy of the box and cylinder is 0 and if only...

I'm trying to learn some physics on my own, using the internet as my main source of information. Now, I'm a bit confused about some terminology, and I can't find anything about it... Distance vs displacement in rotational kinematics! Is there a similar difference as in linear kinematics...

Homework Statement A barrel is lowered into a boat using the illustrated apparatus. The barrel can be considered to be a uniform cylinder with M=100kg and r=0.40m. The weight on the other end of the rope has m=30kg. Assume that the barrel does not slip against the wall, that the other 2...

Homework Statement Determine the relationship between the angular acceleration of the flywheel, the downward acceleration of the block, and the radius of the ring. Known data: Mass Ring: 1.420 kg Radius Ring (Inside, then Outside): 5.10 cm, 6.325 cm Mass Disk: 1.455 kg Radius Disk...

A flywheel 1.2 m in diameter is uniformly accelerated from rest and revolves completely 68 times in reaching a speed of 125 rev/min. Find the time taken to reach this speed i have been given the correct answer as 65.29 seconds Wht i have up to now ω1 = 0 ω2 = 125 r/min = 125/60 =...

[b]1. Consider a fan that has rotated by a total of 2 complete revolutions from where it started. This quantity (2 revolutions) is analogous to what quantity in linear kinematics? Position Displacement Velocity Speed Time Time Homework Equations I am...

Homework Statement Each of the questions are either increase, decrease, equal, or undetermined. 1) You are sitting on a rotating chair, holding a 2 kg mass in each arm outstretched. When the masses are dropped, your angular momentum -------. 2) You sit in a rotating chair holding 2 kg...

1. A uniform rigid rod of length L and mass M is attached to a frictionless pivot point at one end. The rod is initially held completely horizontal and is released from rest. What is the linear and angular velocities at the instant the rod is in the vertical position?2. -ΔU = ΔK 3. -ΔU =...

Homework Statement An electric turntable 0.710 m in diameter is rotating about a fixed axis with an initial angular velocity of 0.230 rev/s. The angular acceleration is 0.887 rev/s^2. A. Compute the angular velocity after a time of 0.192 s. B. Through how many revolutions has the blade...

Homework Statement A quarterback throws a pass that is a perfect spiral. In other words, the football does not wobble, but spins smoothly about an axis passing through each end of the ball. Suppose the ball spins at 9.0 rev/s. In addition, the ball is thrown with a linear speed of 21 m/s at an...

Homework Statement A spinning wheel on a fireworks display is initially rotating in a counterclockwise direction. The wheel has an angular acceleration of -4.40 rad/s^2. Because of this acceleration, the angular velocity of the wheel changes from its initial value to a final value of -24.0...

Homework Statement A block with mass m is revolving with linear speed v1 in a circle of radius r1 on a frictionless horizontal surface (see the figure ). The string is slowly pulled from below until the radius of the circle in which the block is revolving is reduced to r2. Calculate the...

Homework Statement A 45.0-cm diameter wheel, consisting of a rim and six spokes, is constructed from a thin rigid plastic material having a linear mass density of 25.0 g/cm. This wheel is released from rest at the top of a hill 52.0m high. a.) How fast is it rolling when it reaches the...

Homework Statement Summary: The pulley in the figure has radius (R) and a moment of inertia (I). The rope does not slip over the pulley, and the pulley spins on a frictionless axle. The coefficient of kinetic friction between block A and the tabletop is \muk. The system is released from...

Homework Statement A thin uniform rod of mass (M) and length (L) is bent at its center so that the two segments are now perpendicular to each other. a. Find its moment of inertia about an axis perpendicular to its plane and passing through the point where the two segments meet...