The tag has no usage guidance.

learn more… | top users | synonyms

1
vote
1answer
20 views

Four bar linkage moment transmission

The question is. I know the angular velocity of $d$ after applying dynamic mechanics and the constant angular velocity of $b$ of $2\pi\ \text{rad/s}$ and I know the input moment of the power source ...
0
votes
0answers
18 views

Determine the point at which moment vector is zero on a 3D body

I have information about total force and moment on a body for three points, whose coordinates I know. From this information I would like to determine the point at which moment would be zero. ...
-1
votes
1answer
45 views

What is a moment/torque?

What is a moment/torque? i know the formulas m = fxd (Nm), I know how it works, what is does etc. But think of it fundamentally, how is it possible, that a force becomes greater when the arm of an ...
0
votes
0answers
21 views

Bending moment in composite beam with internal “active” stress

I am looking at a problem of a bending composite beam with a symmetric cross -section, $A(s)$. Above the neutral axis $s$ is material $U$ and below the neutral axis is material $L$. $U$ has an ...
0
votes
1answer
33 views

How can I work out tensions using moments? [closed]

If you were given the weight of a metre rule, its weight and the distance between 2 vertical rods holding it up, how would you work out the tension in the rods using the concept of moments or vectors? ...
0
votes
1answer
46 views

Finding the coefficient of friciton [closed]

I'm asked to find the coefficient of friction before the bar starts sliding. Here is my solution -> ∑M = 0 -mg * 1.4863 + 1.8159*T = 0 (T*1.8159) i found by using a cross product ( -2.9726i+ ...
0
votes
1answer
27 views

Finding the friction before slipping [closed]

There is a string that is attached to a bar as shown below in the picture. What is the coefficient friction between the bar and floor before bar starts slipping. I have chosen a pivot point about ...
0
votes
1answer
63 views

Need help understanding angular acceleration due to gravity

The question asks what the angular acceleration of an uniform disc of radius $R$ rotating about an axis passing through its edge if it is released from rest with its center of mass at the same height ...
0
votes
1answer
119 views

Why are inclined push-ups harder?

I came up with a random question which looked simple, but I can't work out the answer. The question is, why are inclined push-ups harder? And by inclined push-ups I mean push-ups with your legs on a ...
0
votes
0answers
40 views

Moment of Inertia of a Motion Simulator Frame

I have a rather specific question. I'm trying to build a motion simulator for flight and racing sims, similar to this: https://www.youtube.com/watch?v=JQAZB3EnI_w . The basic concept is a platform ...
0
votes
3answers
46 views

Multi-Force Lift

Background: I am creating a 3D game. A ship has 3 thrusters that apply force up (Z+) to counteract the force of gravity (Z-). I am trying to figure out how much thrust to apply to each thruster to ...
1
vote
0answers
43 views

Am I approaching this correctly? [closed]

The force system consists of 3 forces and a couple. If the resultant of this system is 100 N downward at point O, determine the couple C in N-m. Let's say point O is at (0,0), at (1,0) a force P is ...
-1
votes
1answer
30 views

Why can't we have more than 3 moment equations in equilibrium equations

Excuse me for a kind of stupid question but, In statics of a 3D rigid body, the equations to determine equilibrium are at most 6 (Fx Fy Fz Mx My Mz = 0) (not counting those from hinges and rollers). ...
0
votes
1answer
110 views

Moments and forces, when part of the scenario involves a circle or arc rather than a straight line

Some questions below, involving strategies, regarding the following problem: A hoop of weight $20$ Newtons can rotate freely about a pin fixed in a wall. A string has one end attached to a pin, ...
0
votes
1answer
71 views

Resultant center of rotation due to multiple moments

Say, there are multiple moments (M1, M2, M3) acting on a body (of irregular shape) at points P1, P2, P3 respectively. The body is free to rotate about any point. Now, which resultant center (the ...
-1
votes
2answers
62 views

How is electric dipole moment analogous to mechanical moment?

Diplole moment is q*2l. I don't understand the similarity between dipole moment and ordinary mecanical moment.
2
votes
0answers
152 views

Moment line of action

I am having trouble understanding a moment's line of action. Lets say we have door hinge of $L$ length and push down on it with $X$ force. The moment at the begin $(O)$ of the hinge would then be ...
0
votes
1answer
52 views

Bending moments when lifting houses

I have a 3km-wide square with a tower in each corner (A,B,C,D). On edges AB and CD there are level rigid massless beams supported by the towers. A third beam lies on these two, parallel to BC (i.e. ...
2
votes
2answers
86 views

Wheelie physics part 2

Okay, so I got some really great advice from the community here but I am still hung up on some conceptual problems. I posted earlier trying to determine the axis that a bicycle rotates about when ...
3
votes
2answers
559 views

How does a wheelie work?

So I've been trying to create a mathematical model for an electric motorcycle and began to wonder about the maximum possible torque that could be supplied to the rear driven wheel without having the ...
-1
votes
1answer
44 views

What does $\bar{x}_{\textrm{el}}$ represent?

In the context of centroids and moments, what do $\bar{x}_{\textrm{el}}$ and $\bar{y}_{\textrm{el}}$ represent? For example: $$\bar{x}L = \int \bar{x}_{\textrm{el}}dL$$ Some references that use ...
1
vote
2answers
69 views

Need derivation of a formula related to determination of moments of a object about $x$-axis and $y$-axis

I'm given a plate,its density $\rho$ and it is the region bounded by the two curves and on the interval [a,b].I want to find the center of mass of the region below. I’ll first need the mass of ...
0
votes
1answer
327 views

Calculate reaction forces, bending moments and shear forces, udl=0.5kN/m

i have reaction forces of Ra $= 7.890625N$ & Rb $=1 03.359375N$ my shear force calculation equates to 0N at 5.5m which i believe is correct however i am having trouble getting the bending ...
5
votes
3answers
1k views

The momentum of a swinging sword

Suppose you are faced with a zombie, and the only way to kill it and save yourself is to chop its head off with your sword. However, you are very weak from illness, and can only afford to strike once. ...
0
votes
1answer
181 views

Torsional spring and Euler angles

I have a question about the moments generated by torsional springs. Consider an inertial reference frame A and a body fixed reference frame B. The frames are connected by 3 rotational springs acting ...
1
vote
1answer
118 views

Is the moment-curvature relation for an elastic beam general?

The relationship between the moment and the curvature for an elastic beam is $$M = -EI\kappa$$ Previously, I have only used this with small deflections in static calculations. I am currently working ...
0
votes
1answer
258 views

Downward force applied at center of see saw [closed]

If we are given the length of a see saw of negligible weight, and the weights and distances from the center of the two people on the ends of the see saw, how can we find the downward force being ...
0
votes
1answer
77 views

Determine reactance force of four load cells arranged in two dimensions

I have constructed a "force plate" to reconstruct the location (x,y) of a steady state contact point force f. The system consists of four fixed compression load cells L1, L2, L3, and L4 and a thick ...
3
votes
1answer
122 views

Moments of vibrating string

I have to calculate first 10 moments for vibrating string with damping, but I don't know how to do it. I read about moments and in definition they mention linear system $$x'=Ax+Bu, \qquad y=Cx$$ with ...
0
votes
1answer
1k views

Calculating Resultant Force and Torque

I'm working on a sandbox game that allows the player to build a spacecraft and attach thrusters in arbitrary locations on the hull of the spacecraft. The game is set completely in 2D. (I'm a ...
2
votes
0answers
57 views

Fractional-Order Moments

Commonly seen in physics(and statistics) are the concepts of moments of order zero(mass), one(center of mass), and two(moment of inertia). In statistics a third moment (referred to as skewness) also ...
0
votes
1answer
96 views

Centre of mass, integral

I was answering a question on proving the parallel axis thereom for angular momentum and came across this: $$\int Yy'dm=Y\int y' dm=0$$ Where the position of the center of mass of an object is given ...
1
vote
0answers
350 views

Torque of person on bridge [closed]

Consider a 10 meter bridge that weighs 500 N supported at both ends. A person who weighs 750 N is standing 2 m from the end of the bridge. What are the forces $F_a$, $F_b$ holding the bridgeup at ...
-1
votes
1answer
585 views

How do I know which force to use in moments calculation?

I'm working on some Statics problem, with the method of joints, etc and for all of them, we use sum of moments = 0. However, I'm very confused about which forces I should use to find the sum of ...
3
votes
0answers
302 views

Electrodynamic multipole expansion

I am reading Jackson, Classical Electrodynamics, and I have a question regarding the electrodynamic multipole expansion (with page numbers I refer to the 3rd edition). So on page 409, he gives in ...
1
vote
0answers
90 views

How many padlocks required to make the Eiffel tower fall over?

Yes the title is an odd question, so I will provide a little background! Recently the sheer amount of padlocks on the Pont d'Art in Paris caused a part of its railing to fall off. Similar padlocks ...
4
votes
1answer
239 views

Why is a dipole moment called a dipole moment?

The General Formula for a moment is the following one: $$ \vec{M} = \vec{r} \times \vec{F}. $$ However the formula for a dipole moment is this one: $$ \vec{p} = Q \vec{d}. $$ How comes this is still ...
0
votes
1answer
74 views

Initial velocities of a collision [closed]

This is the question: A car of mass 900 kg and a van of mass 1300 kg collide at a crossroads. Investigation into the collision discloses that the car was travelling south east and that the van was ...
1
vote
2answers
653 views

Is the moment of a force the same about any point?

I know that when a body is is equilibrium There is zero resultant force in any direction, i.e. the sum of all the components of all the forces in any direction is zero The sum of the moments about ...
3
votes
3answers
543 views

Why does the moment of force (aka. torque) depend on the perpendicular distance?

Couyld anyone explain how the lecturer concluded that $$(\underline{r_2} - \underline{r_1}) \times \underline{H} = \underline{p} \times \underline{H}$$
1
vote
0answers
62 views

What will be the direction of the force required on the ball to move the ball up the stairs?

Is this diagram correct? The point of force A is at the farthest distance from the fixed centre O ,so the moment arm CD is greater and therefore,maximum torque would be produced.Is my concept ...
0
votes
2answers
1k views

Calculating axle load in cargo container (pics are included)

I'm current developing cargo loader software, but i have a little challenge with calculating load for each axle when a cargo is placed on container. I know that all axles will be affected (the nearest ...
0
votes
1answer
264 views

Moment around a point in a frame

Note: Both diagrams are 2d(they might look 3d because I drew them manually.) I have a prismatic frame that looks like this: I made a section on the half of the first pillar(the red line represents the ...
1
vote
2answers
1k views

How do I find the tension in the cable from this problem? [closed]

I am trying to find the tension of the cable but I don't know what to do.
0
votes
1answer
3k views

Cylinder rolling down slope problem [closed]

A uniform cylinder of mass $m$ and radius $r$ is rolling down a slope of inclination $\theta$. The cylinder rolls without slipping. You may take the acceleration due to gravity to be $g$. At what rate ...
0
votes
1answer
328 views

Damping Coefficient for a Hydraulic-Controlled Door

I am not very good with physics terms, so please treat me as an ignorant. I am trying to calculate a damping coefficient dynamically for a hydraulic-controlled door that opens and closes due to ...
9
votes
2answers
1k views

Do higher-order mass moments have any physical meaning?

The zeroth moment of mass of an object is simply its total mass. The first moment of mass yields an object's center of gravity (after normalization). The second moment of mass yields an object's ...
2
votes
4answers
507 views

Calculating the torque at a point when a motor is stopped? [closed]

So, I'm trying to solve for the torque $\tau_A$ of a motor. I have attached a strong stick to the motor, like so: I apply a force $F$ on the stick which stops the motor. The distance from the ...
0
votes
3answers
462 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
0answers
481 views

Maximum Shear on a Beam - beam with fixed support on one end and hinge on other end

A beam $\displaystyle 3m$ long with fixed support on one end and hinge on the other end is subjected to a uniform load of $10\ kN/m$. What is the maximum shear of this beam? The solution is this one: ...