A tag for questions about the mechanical interactions of rotating objects, including torque and angular momentum.
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Mechanics: collision & rotation [closed]
A rod AB of mass M and length L is lying on a horizontal friction less surface. A particle of mass m traveling along the surface hits end A of the rod with a velocity 'v' in a direction perpendicular ...
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2answers
113 views
Rolling ball which slips
A bowling ball of mass $M$ and radius $r_0$ is thrown along a level surface so that initially ($t = 0$) it slides with a linear speed $v_0$ but does not rotate. As it slides, it begins to spin, and ...
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735 views
DC Motor Torque Constant
I am very new to DC motors and to stackexchange. Please correct me if anything I said does not make sense.
For DC motors, the equation looks like this:
$P = \tau\dot{\theta}$
where $P$ is power, ...
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95 views
Forces on hinge point [closed]
A rod of mass M and length L is initially vertical and is hinged about a point $P$. The point $P$ moves horizontally with acceleration equal to $g$, where $g$ = Earth's gravitational pull . Find the ...
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Help course exercises vol.1 Cap Berkeley. 6 [closed]
1 2. Angular momentum of tetherball. The object of the game
tetherball (Fig. 6.24) is to hit the ball hard enough and fast
enough to wind its tether cord in one direction about the
vertical post to ...
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297 views
How to find Rotational and Translational Equilibrium of Hanging Masses on a Bar?
I am making a hanging mobile which needs to be done mathematically by calculating torque. The problem is, I can't seem to figure out how to solve for the distance of the two masses from the pivot ...
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129 views
Torque required to spin a disk along its diameter
How would I calculate (or simulate) this? I am only interested in the aerodynamic drag caused by the surface moving, not any other forces.
As far as I know, the only variables needed are the drag ...
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Assume a spool rolls down a slope with its body (not its ends) in contact with the slope
I was doing a little mental exercise and imagined the above scenario. I can intuitively see that in the described case, the smaller the diameter of the spool body, the larger the proportion of the ...
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242 views
How does the Commutator and Brushes causes flip? [closed]
I'm trying to make a simple electric motor just for fun project. I've reading this article to understand how an electric motor works. So far, I have been able to make something like as seen in picture ...
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322 views
How to design a hand rotate dynamo [closed]
I want to make a dynamo which can produce electricity. My requirements for the dynamo are as follows.
I need to charge my laptop through this.
I want my laptop to run for 1hour with this energy ...
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0answers
79 views
How long will the bar to travel 1.50 cm threaded rod? [closed]
A threaded rod with 12.0 turns / cm and 1.18 cm in diameter is mounted horizontally. I screwed a threaded rod with a hole to attach to the bar. The bar rotates at 237 revolutions / min. How long will ...
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525 views
Rolling on an inclined plane [closed]
Let us consider a sphere. let it be released from rest from the topmost point of an inclined plane. Now let it come to a rolling motion, after a time x seconds. We can say that at time t= x seconds ...
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2answers
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What are the ideal centers of mass and rotation for a steadicam?
For those who don't know what a steadicam is, I'll explain it in two points to give a basic idea. If you know what a steadicam is, skip to point 3.
1) A steadicam is a stabilizing mount for a motion ...
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1answer
87 views
Confusions about rotational dynamics and centripetal force
I am a high school student. I am having confusions about the centripetal force and rotational motion . I have known that a body will be in rest or in uniform velocity if any force is not applied. But ...
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1answer
519 views
Moment of inertia of a sector about its center point?
What is the moment of inertia of a pizza slice that has a radius r, an angle (radians) of theta, and a height of h about the center point perpendicular to the cheese plane?
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1answer
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A rod of length $L$ & mass $M$ is rotating in a circle about one end then calculate tension in the rod at a distance $x$ from the support
A rod of length L & mass M is rotating in a circle about one end then calculate tension in the rod at a distance 'x' from the support ?
For its solution why should we take mass of L-x portion of ...
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1answer
110 views
Can an electric motor force angular momentum not to be conserved in an isolated system?
An ice skater is in a spin, she pulls her arms in and she spins faster, she lets her arms extend outward and then she starts to slow down.
She will probably weigh on a weigh scale about the same ...
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1answer
94 views
How to find replacement function of a mass?
I wonder how I can find the replacement function of the center of the blue mass? The center of mass of the blue mass is $(0,0)$ and the blue mass is homogeneous. The masses do not move at t=0 in the ...
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1answer
70 views
A mechanics question of finding maximum K.E [closed]
The question is in the diagram as well the diagram
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5answers
256 views
Does the rotational speed of a planet consistently become faster and faster given that there are no conflicting events? [closed]
Does the rotational speed of a planet consistently become faster and faster given that there are no conflicting events?
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2answers
189 views
Which Axis of rotation?
Let us consider a body , A, of arbitrary geometrical shape of mass m1. Now let it be translating with a speed v. Let us consider a small point particle ,P, of mass m2. Suppose it strikes A with a ...
