Tagged Questions
-2
votes
0answers
46 views
Rotating pipe with bug [closed]
A thin mass less horizontal pipe rotates about a vertical axis with angular speed $ω$ as shown in the figure. A small bug, located at a distance $r$ from the axis, starts crawling inside the pipe at ...
0
votes
0answers
18 views
Stability of trajectory of disc which moves along a straight curve
Let's have a disc which moves along a straight curve on a plane in a uniform gravitational field. There need to discover the stability of it's trajectory.
I represented the possible deviation of the ...
1
vote
3answers
65 views
Maximum angular velocity to stop in one rotation with a known torque
I have an object I can rotate with a given torque. I would like to stop applying torque once I've reached a defined maximum rotational speed. The maximum rotational speed should be defined so that ...
0
votes
0answers
39 views
Simple Calculus angular velocity problem [closed]
I have a Lagrange equation and I have no idea why the solution note I looked at have got
$d \over {dt}$$(mr\omega) = Q$,
$d \over {dt}$$(mr\ddot\omega) = Q$.
I had
$d \over {dt}$$(mr\dot\omega) = ...
0
votes
1answer
28 views
A rod of length $L$ & mass $M$ is rotating in a circle about one end then calculate tension in the rod at a distance $x$ from the support
A rod of length L & mass M is rotating in a circle about one end then calculate tension in the rod at a distance 'x' from the support ?
For its solution why should we take mass of L-x portion of ...
0
votes
1answer
146 views
How is torque equal to moment of inertia times angular acceleration divided by g?
How is the following relation true
$$\tau = \large\frac{I}{g} \times \alpha$$
where $\tau$ is torque,
$I$ is moment of inertia,
$g= 9.8ms^{-2}$,
and $\alpha=$ angular acceleration.
0
votes
1answer
78 views
Calculating the moment inertia for a circle with a point mass on its perimeter
I want to calculate the tensor of the moment of inertia. Consider this situation:
The dot represents a points mass, in size equal to $\frac{5}{4}m$. $m$ is the mass of the homogenous circle. I'm ...
-1
votes
1answer
117 views
Confusions about rotational dynamics and centripetal force
I am a high school student. I am having confusions about the centripetal force and rotational motion . I have known that a body will be in rest or in uniform velocity if any force is not applied. But ...
0
votes
1answer
39 views
Rotational Kinetic Energy of a rigid root - Full workings Provided?
Part v is where I'm stuck.
Here is the question with my workings
If I can find Torque I can find L and using the equation $L=Iw$ I can find the w value and hence using $w=2pi*f$ I can prove it ...
0
votes
0answers
37 views
Mechanics: collision & rotation [closed]
A rod AB of mass M and length L is lying on a horizontal friction less surface. A particle of mass m traveling along the surface hits end A of the rod with a velocity 'v' in a direction perpendicular ...
0
votes
3answers
81 views
Mass equals Moment of inertia when constant density?
I have found equation for moment of inertia $(J)$. I'm calculating $J$ for hemisphere, with rotational axis $Z$.
$$ J = \iiint\limits_V r^2 \cdot \rho \cdot dV $$
But if $\rho$ is constant ...
0
votes
2answers
72 views
What's the motion of this yoyo under external force will be?
A yoyo on a horizontal table is being pulled by a string to the right, the table is not frictionless. If we only know that the object doesn't slip, how do we know if the string is winding up or ...
1
vote
1answer
106 views
Moment of inertia of a yo-yo
Considering the yo-yo like two CDs with a hollow cylinder between them, what is the moment of inertia of that object?
The axis that I must choose can't pass through the CM and be parallel to ...
1
vote
1answer
165 views
Cylinder rolling down an inclined plane held by a string
A cylinder of mass M and radius R is in static equilibrium as shown in the diagram. The cylinder
rests on an inclined plane making an angle with the horizontal and is held by a horizontal string
...
1
vote
0answers
281 views
Neglecting friction on a pulley?
So, this is how the problem looks:
http://www.aplusphysics.com/courses/honors/dynamics/images/Atwood%20Problem.png
Plus, the pulley is suspended on a cord at its center and hanging from the ceiling.
...
0
votes
0answers
100 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 ...
0
votes
0answers
67 views
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 ...
1
vote
0answers
252 views
Rotational Dynamics Problem-Rod slipping against block
A uniform rod of mass m and length l is pivoted at point O. The rod is initially in vertical position and touching a block of mass M which is at rest on a horizontal surface. The rod is given a slight ...
1
vote
1answer
260 views
Kinetic Energy And Rotational Motion
The problem is, "A metal can containing condensed mushroom soup has mass 220 g, height 11.0 cm and diameter 6.38 cm. It is placed at rest on its side at the top of a 3.00-m-long incline that is at ...
0
votes
1answer
298 views
Finding Rotational Kinetic Energy Of A Clock
The problem I am working on is:
"Big Ben, the Parliament tower clock in London, has an hour hand 2.70 m long with a mass of 300 kg, and a minute hand 4.20 m long with a mass of 100 kg (see figure ...
0
votes
2answers
2k views
Tensions And Pulleys With Masses
The problem I am working on is:
"A block of mass m1 = 1.80 kg and a block of mass m2 = 6.30 kg are connected by a massless string over a pulley in the shape of a solid disk having radius R = 0.250 m ...
0
votes
2answers
264 views
Setting up equations for a Rotational Kinematics system
I'm having a hard time setting up equations for the following problem:
A green hoop with mass $m_h$ and radius $r_h$ m hangs from
a string that goes over a blue solid disk pulley with mass $m_d$
...
0
votes
1answer
112 views
Deducing latitude from Foucault Pendulum
Suppose I set up a Foucault pendulum and observe that it precesses at a rate of 216.528 degrees per day. While I am observing this, a total solar eclipse occurs. Where am I, and what is the date?
My ...
0
votes
2answers
249 views
Force applied off center on an object
Assume there is a rigid body in deep space with mass $m$ and moment of inertia $I$. A force that varies with time, $F(t)$, is applied to the body off-center at a distance $r$ from its center of mass. ...
0
votes
3answers
2k views
Finding Angular Acceleration of rod given radius and angle
A uniform rod is 2.0 m long. The rod is pivoted about a horizontal, frictionless pin through one end. The rod is released from rest at an angle of 30° above the horizontal. What is the angular ...
3
votes
1answer
129 views
Angular acceleration of stone disk
I have a conceputal question regarding the following problem:
A round massive stone disk with diameter $0.600 m$ has a mass of $50.0 kg$. The stone rotates at an angular velocity of $115.2 rad/s$, ...
1
vote
1answer
169 views
What controls whether a ball will skid or roll?
A billard ball is struck with a cue. The line of action of the applied impulse is horizontal and passes through the center of the ball. The initial velocity $v_0$ of the ball, its radius $R$, its mass ...
1
vote
2answers
407 views
In a circular pendulum, where does the equation $v=\sqrt{rg\tan{\alpha}}$ come from?
In a circular pendulum
the $v$ of the particle is $$v=\sqrt{gr\tan{\theta}}$$ where $r$ is the radius and $g$ is the gravity(positive sign), which is equal to ...
0
votes
1answer
87 views
Period of an Object in Periodic Motion
My attempt (if it matters):
The initial period is given by $T_X = \frac{2\pi X}{v}$ for some $v$.
The new period is given by $T_Y = \frac{2\pi Y}{v}$ for the same $v$.
$Y = \frac{X}{2}$, so ...
0
votes
2answers
503 views
How to interpret this vertical circular motion problem?
A bucket of water is tied to a rope and swung in a vertical circle.
The distance from the bucket centre to the axis of rotation is
$2.08m$. Calculate the angular velocity (in $rad s^{-1}$) of ...
1
vote
1answer
266 views
What techniques can be used to analyze a rod rotating about the edge of a table?
A uniform rod of length $4x$ is rotating
about the edge $O$ of the table. (The rod does not fall off the table.) The centre of mass $G$ of the rod is distance $x$ away from $O$. The rod is making ...
-1
votes
1answer
71 views
A mechanics question of finding maximum K.E [closed]
The question is in the diagram as well the diagram
1
vote
3answers
539 views
Work Done by Rockets in Orbital Motion
A weather satellite ($m_s = 4350$ kg) is in a stable circular orbit around the Earth ($m_E = 5.97 \cdot 10^{24}$ kg). It completes an orbit once every 2 and a half hours.
(I'm sure about these 2 ...
0
votes
1answer
358 views
Calculation for force generated by a rotating rectangular blade
When trying to calculate the lift force generated by a simple rectangular blade, I've found the following equation: $$F = \omega^2 L^2 l\rho\sin^2\phi$$ in which $\omega$ is the angular velocity, $L$ ...
1
vote
2answers
415 views
Moment of inertia of a coin
I have a a coin infinitely thin, rotating along the diameter.
How to derive the formula for it's moment of inertia passing through the diameter.
I was suggested to use the surface density and ...
-1
votes
1answer
98 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 ...
-1
votes
1answer
532 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?
1
vote
4answers
669 views
17 Joules of Energy From a Mouse Trap
Do you think it would be possible to get 17 joules out of a standard size mouse trap. By my math, it is a torsion coefficient of 3.45 or so out of the spring.
0
votes
1answer
183 views
Angular velocity $\omega$ by $v$
We have two girls, with mass (M). They become close to each other in speed of V. The distance between them is 3L.
I was asked to calclute the Angular velocity (w) of the two girls. So I set the ...
0
votes
2answers
187 views
Problem based on Rotational Motion #2
One fourth length of a Uniform Rod of mass $m$ and length $x$ is placed on rough horizontal surface and it is held stationary by means of a light thread as shown in the figure. The thread is brunt ...
1
vote
1answer
229 views
Problem based on Rotational Motion [closed]
A spool of mass $\mathsf m$ and inner radius $\mathsf r$ and outer radius $\mathsf{2r}$, having moment of inertia $\Large\mathsf{\frac{mr^2}{2}}$ is made to roll without sliding on a rough ...
1
vote
0answers
187 views
How to model an accelerometer measurements on a car wheel?
I am working on kinematically modelling an accelerometer on a car wheel.
When working on the initial conditions, I am confused whether or not I should use the gravitational acceleration since there ...
0
votes
0answers
81 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 ...
2
votes
1answer
439 views
Lean angle of a turning bicycle
I'm asked to derive a relationship for the leaning angle of a bicycle with the following specs:
Center of gravity for bike and rider is a distance $L$ above the ground when vertical, and the total ...
1
vote
1answer
201 views
Top spun up with string under tension problem [duplicate]
Possible Duplicate:
Homework about spinning top
I have a top with an unknown mass. It has a moment of inertia of 4.00 * 10^-7 kgm^2
a string is wrapped around the top and pulls it so that ...
3
votes
2answers
1k views
How to calculate cord tension in a vertical circle?
Mass m is connected to the end of a cord at length R above its rotational axis (the axis is parallel to the horizon, the position of the mass is perpendicular to the horizon). It is given an initial ...
1
vote
1answer
696 views
Finding angular acceleration from torque
We have to analyze this video
Givens:
An applied net torque due to the wind on the windmill is equal to 1500 N*m.
Each (of the 3) propeller props weighs approximately 45 Kg and has a Moment of ...
