Tagged Questions
0
votes
1answer
86 views
Problem solving moments in equilibrium
Two straight ladders, AC and BC, have equal weights $W$. They stand in equilibrium with their feet, A and B, on rough horizontal ground and their tops freely hinged at C. Angle CAB = 60$ ^o$, angle ...
0
votes
1answer
31 views
Find the bending moment of a pole attached to a moving block
I'm having trouble with the following problem.
What I've done so far:
x-y is the usual coordinate system.
$a=\frac{F}{m}=\frac{800}{60}$ and the y component of this is $a_y=a\sin{60^\circ}$.
To ...
0
votes
0answers
72 views
Tension $T$ in cable [closed]
Calculate the tension $T$ in each cable, as well as the magnitude and direction of the force exerted on the strut by the pivot in each case mostrados.En systems, w is the weight of the suspended box, ...
0
votes
0answers
27 views
How do I minimize the the stress created by fore-aft forces?
My friends and I are designing a bench press spotter. Essentially, when the user needs help lifting the barbell due to muscle fatigue, an arm on each side of the user raises to provide assistance. ...
1
vote
2answers
100 views
Additional mass of block on inclined plane
I would like some help in solving this problem.
Height is 15 cm , base is 88 cm
My attempt:
$$(119.3 + m)(\sin(\theta)) = (88*9.8)$$
$$ 15^2 + 88^2 = 89.269^2 $$
$$ \sin^{-1} = 15/89.269 $$
$$ ...
1
vote
0answers
54 views
How can I calculate all of the tensions in the cords? [closed]
I have been stuck on this problem for the last half, and to be honest I don't even no where to begin. I'm being asked to calculate all of tensions for the cords. I know I'm supposed to use $\cos$ to ...
0
votes
3answers
133 views
Doubts with levers
I'm studying for a test of static rigid body and I'm having doubts on how to solve problems involving levers with weight.
If I have, for example, a lever 10 kilograms and 3 meters long and one support ...
1
vote
1answer
431 views
Solving a Statically Indeterminate Truss with Energy Equations (Tricky)
Okay, first off, I know that there is a very similar problem about statically indeterminate trusses here, but my problem was a bit different and I didn't know how to adapt the answer for that problem ...
0
votes
1answer
622 views
How to calculate the supporting force for a cantilever beam? [closed]
How do I find the supporting force $R_A$ and the moment $M_A$?
Should I use the sum of moments or?
0
votes
1answer
186 views
Trying to understand the tension in a spring with two weights attached [duplicate]
Possible Duplicate:
Why I think tension should be twice the force in a tug of war
For (A) in this image, I would think the tension should be should be 2mg.
However, my book says the ...
0
votes
1answer
211 views
Can I use Newton's second law to solve what seems to be a torque problem?
The Problem:
An 8-m-long beam, weighing 14,700 N, is hinged to a wall and supported by a
light rope that is attached 2.0 m from the free end of the beam. If the beam is
supported at an angle ...
3
votes
1answer
559 views
If 1 screw can support 120 lbs, how much weight can 25 screws support?
While this is mainly about my personal home improvement project, I figure this would be a good opportunity for some of you to apply your physics skills to a real-world situation.
My situation is ...
0
votes
1answer
275 views
Torque and equilibrium
I am a little stuck on the concept involved in part b) of the following problem:
A $5 m$ long road gate has a mass of $m = 15 kg$. The mass is evenly distributed in the gate. The gate is supported at ...
3
votes
1answer
354 views
Understanding moments as forces?
I was watching this lecture on analysis of stress for mechanics of materials. At time 7:20, the lecturer says that in equilibrium, the sum of forces and "moments" in each direction (x,y,z) must be ...
0
votes
1answer
326 views
Calculating torque in a structure
I posted this on math stack exchange but realize it is more a physics question.
I have a structure which is set up as shown in the image. A weight hangs from point A with mass $m$. Joint B is free ...
2
votes
1answer
274 views
Why does the beam in a weighing balance get tilted proportional to the weights added to each pan?
I'm talking about a beam balance(a simple weighing balance with a beam and two pans hung on either side)
As answered in a previous question, the beam comes back to the original position when one ...
0
votes
2answers
177 views
Hanging a Hammock
I have a hammock that I want to hang using a tree on one end and a wooden post set in a bucket of cement on the other end.
How would I determine how heavy the cement needs to be so that it would ...
2
votes
2answers
848 views
Angles on swing sets
I'm building a swing set for my children. All of the designs I've seen involve building two A-frames and connecting them at the top with a crossbar/beam from which hang the swings. The A-frames are ...
3
votes
3answers
709 views
Deadlifting the rear end of a car with a lever. What it equates to in actual weight?
Consider this youtube video of a guy lifting a car. (skip to 2:15).
I checked, and these cars (PT Cruiser) weigh $1417\:\rm{kg}$. What would the equation be to estimate how much weight he is actually ...
0
votes
1answer
361 views
Can anyone solve this simple static equilibrium problem? [closed]
A bridge is 50m long, has a mass of 20,000kg, and rests on two pivots, A and B. The distance between A and the left side of the bridge is 10m. The distance between B and the right side of the bridge ...
2
votes
0answers
539 views
Forces and torques about the CENTER OF MASS of a physical pendulum
I'm currently stumped by the following situation. Say we've got a rectangular physical pendulum (think ruler with a hole-punch at one end).
It's trivial to analyze the motion of the pendulum with the ...
-1
votes
1answer
122 views
Find largest angle
The two homogeneous bars AB and BC are connected with a pin at B and
placed between rough vertical walls. If the coefficient of static friction between
each bar and the wall is 0.4, determine the ...
1
vote
1answer
129 views
Finding the contact force in a mechanical problem [closed]
what is the proper FBD for this system. I cant decide since the weight is given, but there is tension and contact forces. Things get mixed up.
Determine the contact force between the smooth 200-lb ...
1
vote
1answer
162 views
Wave equation from hooke law - simple question
In the paragraph http://en.wikipedia.org/wiki/Wave_equation#From_Hooke.27s_law
it is said, regarding the u(x) function, that
Here u(x) measures the distance from the equilibrium of the mass
...
0
votes
2answers
1k views
How do I find the tension in additional strings in this problem?
A mass of 5.00 kg hangs attached to three strings as shown in the figure (see image below). Find the tension in each string. Hint: Consider the equilibrium of the point where the strings join.
...
0
votes
1answer
444 views
Solving an indeterminate triangle truss structure (statics)
From the setup of two trusses as shown in this illustration, how can I solve for the axial reaction forces in the trusses, and in the points A and B (Ax, Ay, Bx, By)? It is assumed that the joints ...
4
votes
1answer
510 views
Hooke's Law question
I have the following question to answer:
a force of160 N stretches a spring 0.050m from its equilibrium position.
A. what is the spring constant of the spring?
The equation for Hooke's Law in my ...
1
vote
2answers
558 views
Calculate the weight a simple plank can support
I'd like to build a simple desk; just a single plank of wood (or a few side-by-side) with solid supports on each end of the desk. What I'm trying to figure out is how thick a plank I want to use for ...
7
votes
2answers
2k views
What is the force on the arms in a pushup?
What force do the arms have to generate to do a pushup? Let us look a this simplified model:
The body can be represented by the green plank of mass B. Its angle to the ground is $\theta$.
This ...
2
votes
2answers
978 views
Distribution of forces
(little background: I'm trying to develop a small, quick 'n dirty static physics engine to determine whether a stacking of boxes is stable).
If I have a 3D rigid box (with the bottom in the ...
1
vote
4answers
1k views
Upward force on a object at rest
Is there an upward force on a object at rest? If yes, where does it come from?
3
votes
5answers
496 views
How much force would be necessary to hold a 6-foot steel staff weighing 20 lbs from one end of it, parallel to the floor?
This isn't a homework problem. I'm asking cause I'm wondering how strong a person would have to be to pull it off. Their arms would be extended, both hands gripping the staff at one end, and the staff ...
