Questions tagged [applied-mechanics]
Questions about using applied mechanics to model engineering problems.
284
questions
3
votes
1answer
51 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
46 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 ...
1
vote
3answers
86 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 ...
1
vote
3answers
170 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 ...
0
votes
1answer
43 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 ...
1
vote
3answers
70 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 ...
0
votes
2answers
42 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 ...
0
votes
3answers
52 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
votes
3answers
36 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 ...
1
vote
2answers
56 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 ...
1
vote
1answer
47 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 ...
1
vote
3answers
62 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 ...
0
votes
1answer
47 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 ...
1
vote
0answers
33 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 ...
0
votes
3answers
66 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
votes
2answers
36 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 ...
1
vote
0answers
33 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
votes
1answer
46 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
votes
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 ...
0
votes
2answers
45 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
votes
2answers
73 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
votes
2answers
37 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
vote
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 ...
6
votes
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
votes
1answer
36 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$ ...
0
votes
2answers
55 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
votes
1answer
267 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 ...
1
vote
2answers
42 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 ...
0
votes
0answers
20 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 ...
0
votes
0answers
31 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 ...
0
votes
3answers
151 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 ...
1
vote
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
votes
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
79 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
37 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
votes
3answers
94 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 ...
1
vote
1answer
173 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 ...
0
votes
3answers
72 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 ...
0
votes
3answers
64 views
In circular motion , why do we say this is centripetal acceleration
Let us say a particle is moving in a circle with Uniform circular motion .
Then , if I take an equation like this .
$\theta$ = S(Arc length or Total distance covered ) / Radius of circle *( time ...
4
votes
0answers
38 views
What is the purpose of the ink delivery disks found in most rollerball pens
See picture.
In most rollerball pens there are those peculiar looking disks near the nib, the purpose of which I have not yet figured out, apart from being some kind of ink reservoir/flow control.
...
0
votes
2answers
56 views
Torque required to start rotating a wheel about its center
Assuming i have a circular disc of a significant mass and diameter. Neglecting friction, if a motor is put at its center how do i calculate the torque required for the wheel to just start to rotate?
...
0
votes
1answer
50 views
How to calculate torque required to rotate assembly about the center
The image is a hollow cylinder: 2in OD, 1.76in ID. Connected is an angled bracket, 45 deg, that weighs 3lbs. The top rectangle piece connected to the bracket is 10 lbs,the dimensions are 31.1in x 14....
0
votes
2answers
32 views
Is dimension of angular displacement never degree?
Is units of angular displacement never a degree and is always a radian ?
0
votes
2answers
36 views
Did not understand this regarding angular velocity
It says $V\sin \alpha$ (component of velocity perpendicular to OP) is the cause of angular displacement. How is it?
if only $V\cos \alpha$ existed, we need not turn over head to always to look at a ...
0
votes
0answers
35 views
Gear/Mechanics problem: How to design to allow for 2 types of rotation
I am designing a new mowing system that can effectively mow around poles. The machine consists of an arm that is attached to the back of a tractor and runs off its PTO. At the end of the arm is a ...
0
votes
1answer
22 views
Why are the two acceleration considered as a1 and a2 here and find acceleration of 6kg mass?
Why are the two acceleration considered as a1 and a2 here? What is the reason for this even though the tension of both the strings are same.
T is equal to 5gTcos 53 for left side and 5gTcos37 for the ...
2
votes
0answers
71 views
Calculating the bending moment ($M$) of a beam as it relates to stress ($σ$) and strain ($ε$)?
I am trying to learn how to work out the bending moment for progressively complex systems to model a beam. I am assuming only one axis of motion (transverse = $y$).
For the basic equations of motion, $...
1
vote
1answer
146 views
Determine the reactions on supports A and C and write the functions of the internal forces for the beam sections AB
The figure shows a metallic structure composed of two beams $AB$ and $BC$ connected to each other by a pin in $B$, the structure being supported in A and C through fixed supports. In the AB beam, a ...
1
vote
1answer
46 views
Reinforce foldable table legs
I'm trying to build a table with 4 swivel legs that can be locked into arbitrary angles so that it can stand over one to three rows of storage crates in my garage:
As you can see, the legs aren't ...
0
votes
2answers
127 views
formula for M(x) - Shear Force and Bending Moment Diagrams
I've watched the video "Understanding Shear Force and Bending Moment Diagrams" from "The efficient engineer" and i got a doubt in this exercise
For $4<x<7$ I arrive to $V=-6x+...
