Questions tagged [applied-mechanics]
Questions about using applied mechanics to model engineering problems.
296
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Bar released from upright position rotates about a lower hinge before being caught by a steel cable, how to calculate the tension on the cable?
I wish to check the safety factor of a steel cable that I've designed to catch a heavy bar that rotates freely due to the gravitational force acting on it.
From the upright position, I'm assuming that ...
0
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2answers
29 views
Do tensile and compressive forces have significance only in pairs?
In strength of materials, there are two types of axial forces which can act on a prismatic bar - Compressive and Tensile. Do they significance only in pairs?
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3answers
52 views
Can I create a whirlpool/vortex around a horizontal axis in a flat bottle using motor?
I am using this flat bottle:
I fixed a motor at the centre of one of the flat sides and attached an impeller. I thought this will create some kind of whirlpool effect but as you can guess, since the ...
0
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1answer
67 views
Why is the theoretical formulation not explaining why the graph of the square of the velocity and angular displacement is nonlinear (experimentally)?
So I did a wind tunnel experiment where I put a rope restrained (1 degree of freedom, so it can wave in the direction of the wind) at one end so that it displaces according to the variation in wind ...
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3answers
38 views
Find the maximum stress at a point in a machine member
A machine member having a diameter of 50 mm and a length of 250 mm is supported at one end as a cantilever subjected to different forces as shown in the figure. Find the maximum stress at points A and ...
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2answers
62 views
How long does it take and how far does it travel a sphere in free fall before reaching a percentage of the terminal velocity?
Assume a sphere (hail) that is free dropping in air. At some the sphere will reach close to the terminal velocity. The question is:
how long $t_p$ in seconds does it take before a percentage $p$ of ...
1
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1answer
34 views
Does the terminal velocity of a sphere in free drop increase with increasing diameter?
I was trying today to calculate the terminal velocity of a hailstones with increasing diameter and mass. I was trying to figure out if larger hailstones will have a higher impact velocity or lower.
I ...
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26 views
Computing forces and moments acting on the sides of a rectangular shell element from corner forces and moments
I have a FEM program for shell elements implemented through the direct stiffness method. Using this program corner displacements of shell elements due to external loading are obtained through the ...
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0answers
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Difficulty in understanding polarization? Is it only applicable for H and an electronegative element like chlorine? [closed]
There are two examples I have taken in diagram. In the first one , we have a cation and anion. They form an ionic bond due to which the cation has no electrons and the anion has 2 electrons. There are ...
0
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2answers
88 views
Can a beam be too short to experience bending stress?
The question in the title says it all. I've got a a configuration where I'm using a bolt to support a load. The way its set up, the bolt will have a very short cantilever on it. When I calculate the ...
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0answers
31 views
what is the torque difference in single plate clutch disks and multidisk clutches? [closed]
I have a review question that I am not sure about the answer. The question goes like this:
"In comparison to single plate clutches, multidisk clutches are associated to which of the below notions?...
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56 views
Mounting grinding wheels on a threaded rod
I'm trying to mount a set of 6" grinding wheels on an M12 threaded rod. The problem I have is keeping them perpendicular to the rod so that they don't wobble when they turn.
The wheels have a 1&...
3
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1answer
62 views
How do rollercoaster designers calculate the ideal curve?
I've been looking into rollercoaster track designs and wondered how they mathematically calculate the ideal curves to fit some specific layout without creating excessive Gs or other rider discomfort ...
2
votes
1answer
62 views
Free body diagram of a differential-drive mobile robot
I'm trying to study the free body diagram of this differential-drive mobile robot in case of straight trajectory (same torque applied on both of rear wheels) and pure rolling motion
I started ...
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3answers
99 views
How can you control the speed of a rope moving through a pulley?
I'm putting together a ceiling-mounted clothes rack. The rack is raised and lowered with rope and pulleys.
If the rack is raised under full load and accidentally released, then the system could be ...
2
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3answers
190 views
Do all structures deform if put a load on them?
Suppose I have a concrete wall in front of me and I push on it, now it seems that I do work and the energy has magically disappeared.
I am trying to figure out how this works, the explanation I ...
1
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1answer
47 views
Calculating the diameter of screws that are on radius 160mm from axis of rotation. I need help - I don't know If I'm thinking in the right way
First of all, english is not my first language so if there are some mistakes I made - I'm sorry and I hope everything is understandable.
The example I am trying to solve reads the following:
The gear ...
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3answers
128 views
Why do we write T cos theta = mg for this Q instead of mg cos theta = T
For this Q , the author of the textbook writes that T cos 45 =mg
but it also states that mg cos 45 is not equal to T. I got to know about this because this is the way , I solved it first.
My Q :1 is ...
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2answers
53 views
Effect of centripetal acceleration on angular acceleration
$a_t$ = $\frac{dv}{dt}$ = $\frac{d(r*\omega)}{dt}$ = $r $* $\alpha$.
$a_c$ = r*$\omega^2$ = $\frac{v^2}{r}$
These are almost all the variables and values associated with centripetal and tangential ...
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3answers
55 views
How to guess direction of friction in any case
Here , in case of a death well situation as an example.
Q How is direction of friction going to be opposite to mg or in upwards direction ?
Why not:
In case of like circular turning , direction of ...
0
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3answers
38 views
Is there any frame of reference in which we can neglect the gravitational force?
There is a laboratory in which there is a string tied to a bob on the earth.Consider the earth is perfect sphere ,rotates on its own axis in a circular path with uniform angular velocity. Main Q of ...
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2answers
59 views
What size feet for this wind-protection panel?
I need to create a series of free-standing perspex panels to add height to an existing fence for wind-proofing purposes.
My idea is that each panel would be fixed to two supporting poles that are ...
2
votes
1answer
50 views
Degree of freedom of a mechanism
A mechanism popped up in my mind when I was studying kinematics, see picture below
$J1,\ J2,\ J3$ are rotational joints and there are two translational joints $J4$ and $J5$ between two sliders and the ...
2
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3answers
86 views
Would a car slip down on a frictionless banked road and situation for friction road
Here , we have a car on a banking road. Considering two cases :
Frictionless and friction surface of the road.
I give an initial velocity to the car by a push for a second. Then , the cases discuss ...
1
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1answer
64 views
How to generate a repeating semi-circle waveform using a mechanical linkage
How can one, in a smooth way, produce a semicircle wave, as opposed to a sinusoidal wave ?
Imagining the machinery and linkages behind the movement.
I mean the trace. For example a point fixed in ...
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0answers
50 views
How is a plank able to stop a spring door [closed]
So , here we have door which can get closed on its own due to spring. Agenda of Q is to put sth beside the door so that the door does not close .
The Q tells us that when we put a brick of 0.5kg. Door ...
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vote
3answers
80 views
Why do I get pushed back when I’m in a car at high speed?
When I’m in a car at high speed , I get kind of like pushed back if I’m sitting on the cars seat. How does it happen and why ?
If I’m in a car , then I have the same speed as car and for the car , I ...
0
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2answers
50 views
Find minimum horizontal force required to keep the block and wedge stationary?
In the adjoining figure, the coefficient of friction between wedge (of mass M) and block (of mass m) is μ. Find the minimum horizontal force F required to keep the block stationary with respect to ...
2
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0answers
37 views
Magnetic Force - Point of Load
I am using a Magnet like this in an assembly and I am trying to calculate the torque in point P2 (see picture below) resulting from the attraction force F between my magnet and the steel part.
As I ...
0
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1answer
54 views
Find a constraint relation for this Q of 3 pulleys and 2 blocks attached with string
Using any method find the constraint relation between mass 1 and mass 2.
Assumptions: No friction , massless string and pulley.
Q: Find constraint relation between 1kg and 2kg block.
what I tried so ...
0
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2answers
52 views
Why is the acceleration of wedge and block equal like this
No friction at all anywhere. Let me explain the diagram in steps and the Q.
green colour let us start with. It represent a wedge on which there is mass of 10kg (red colour). That’s it the first ...
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2answers
55 views
Find the acceleration of a block relative to incline plane in non and inertial frames?
A block can slide on a smooth inclined plane of inclination $\theta$ kept on the floor of a lift. When the lift is descending with retardation i.e. $ a \; m/s^2 $. Find the acceleration of the block ...
0
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2answers
76 views
Why does the 1kg mass move towards inclined plane here?
Assumption :All frictionless surfaces.
EDIT: In the book , it doesn’t say friction has to be present but as PeteW has mentioned , i think it should be necessary too. So , in that case let me take two ...
0
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2answers
38 views
Why is the tension on mass m1 not 2T here?
I have named the strings as S1,S2 and S3 on diagram. T is the tension in the string.
If I draw the Free body diagram for m1, I think it should be 2T force on it but on internet , it is just T. So , ...
1
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1answer
45 views
Any idea on how to prove this formula of tension?
The formula is:
$$T= \dfrac{\left(\sum (\text{coefficient of tension})_i\right) \cdot g_{effective}}{\sum \frac{(\text{coefficient of tension})_i^2}{m_i}}$$
I tried to prove this formula but not ...
7
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2answers
2k views
How do suction cups work?
These are suction-mounting hooks. I want to visualize and understand how do they stick on walls.
After these hooks stick on wall. Like we compressed them. How? Since gases are compressible up to a ...
2
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1answer
44 views
Firing a bullet on wooden block and then finding the average resistive force by block?
For a Q in which we are firing a bullet of 0.04kg onto a wooden block which is stopped after a distance of 60cm after penetrating inside it. It’s u=90m/s.
For this Q , we can find a=-6750m/s^2. Using$ ...
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2answers
60 views
Why is final momentum found by two formulae in case of increasing force not equal?
So, let us say a body moves with 10 m/s, mass = 10 kg.
At time t=0 a force of 30 N is acting on it. Gradually (linearly) the force increases and finally it becomes 130 N after a period of 2 second .
...
4
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1answer
567 views
Why is the Stress vs strain diagram preferable to the Load vs displacement diagram?
I’m really unsure what is the difference between stress vs. strain and load vs displacement graphs and why stress-strain is better.
I know that the units are different:
stress is in MPa and the load ...
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2answers
43 views
Condition for equilibrium of a rigid body on a horizontal surface
The following question is from a past paper from Further Mechanics and it has been bothering me immensely I have spent hours cracking at a way to make sense of it, the question is in two parts
Part ...
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0answers
23 views
Sprocket Angular Velocity [duplicate]
I have a question please that I need help on.
Consider the chain that is draped over the sprocket with mass moment of inertia of 0.005kgm^2 about central axis. If 4kg block is released from rest from ...
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0answers
32 views
Are there examples of spring-mass-damper system that exhibit increasing growth in an unstable way
Simply, are there examples of spring-mass-damper systems that exhibit unbounded behavior or at least increasing behavior for a period of time. I am trying to do some vibrations research, but I am ...
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3answers
159 views
Force and the reactions on the supports
Consider the movement in the vertical plane of an $AB$ bar with a mass of $20 kg$, $0.8 m$ long and supported by two cursors: one at the end A and the other at point G coinciding with the center of ...
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1answer
34 views
Want to simulate a mechanism with spring in it for forces acting in different direction (Kinematics). How to do it using solidworks or ANSYS? [closed]
Thought of using motion study in Solidworks but not able to account for forces at the different axis in it
here is the image to better understand it. There hasn't been any progress with the ...
2
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1answer
65 views
To stop or to go around?
Let us we are moving in a car. There is a wall in front of us, we need to decide can we go around it or not. It is known that width of the wall is $w$ and our speed is $v = const$.
What is a simple ...
4
votes
1answer
84 views
Determine the aceleration of points B,C and D, angular aceleration of rod and the tension in rope DE when ropes AB suddenly breaks
The solutions are F(DE)=134.38N, a(D)=2.016m/s^2 , α=1.29rad/s^2, a(C)=7.828m/s^2
I agree that the FBD and the KD are these:
Then to solve this problem I've done:
$$\sum M_{c}= I \alpha_{BCD}$$
$<=...
1
vote
1answer
51 views
Why this torque is not considered into the virtual work principle equation?
In the picture above you can see a SCARA robot, with its end effector (the point x,y). The torques c_a and c_b are the ones of the motors in the joints, while f is an external force. My teacher has ...
0
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3answers
95 views
How to solve this Question regarding compound accelerations
So , I was trying to solve it. Then , I notice that acc of 2kg mass has 2effects. One acc from the force to left and one from the Question , it says acceleration to be up. Then , the 2kg mass would go ...
2
votes
1answer
201 views
Determine the angular velocity and angular acceleration of the AB bar at the instant shown
Consider a sliding cursor C that is fixed to the disk which has a constant angular velocity counterclockwise at 4 rad/s. Determine the angular velocity and angular acceleration of the AB bar at the ...
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3answers
73 views
Different results when applying equation
The system shown in the Figure is guided by two blocks in A and B, that move in the fixed grooves. If the speed of A is 2m/s down, determine the speed of B at time θ = 45º
In the textbook they said w ...