# Dynamic Definition and 55 Discussions

Dynamic is an Italian independent record label located in Genoa. Founded in 1978, it specialises in classical music and opera, especially rarely performed works and has produced several world premiere recordings. The Dynamic catalogue contains over 400 titles, with about 25 new titles added each year and is distributed in 32 countries.

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1. ### How to calculate the speed of this umbrella extension arm?

TL;DR Summary: Have a university project where we are calculating the speed of the arm at the end. I need some help on where to start on the calculations. We have tried to determine instantaneous center of rotation for the device. We want to find the linear velocioty of point B. There is a...
2. ### Number of collisions by a bullet

How to find the collision number if the moving bullet hits a few wooden blocks and every collision takes 10 percent of its speed. In which block will the bullet stay?
3. ### Car that undergoes non-uniform circular motion

In the solution manual, it says that: the resultant of friction force is ##<= kmg##, hence $$m\sqrt{\omega_t^2 + (\frac {v^2} {R})^2} <= kmg$$ and from this equation, we will get $$v^2 <= R \sqrt{(kg)^2 -\omega_t^2}$$ which will make ##v_{max}^2= R \sqrt{(kg)^2 -\omega_t^2}## Finally, they...
4. ### I Classical Mechanics - Motion of a particle

Show that a point with acceleration given by: a=c*((dr/dt)×r)/|r|3 where c is a constant, moves on the surface of a cone. This is jut an example to illustrate my doubt. I don't know how to obtain the tracjectory given only the acceleration in this format. I realized that if i can show that...
5. ### The Force components acting on an object

Another user suggested adding the forces in the x and y direction then dividing by 1.4. Doing this for A) gave me 4.285 which was wrong any suggestions?
6. ### A 2.0x10^4 kg rocket has a rocket motor that generates….

I tried A with the solution of 9.73 and 8.69 both wrong.
7. ### Object at rest hanging from two ropes

Here is where I am at : 1- F(C2/P) > F(C1/P) must be true I believe this is false, considering the angle separating C1 from the 'ceiling' is bigger 2- F(C2) > 10 N may be true I believe this is true because F(C2) could be broken down into vector components which may go above 10 N 3- Vector sum...
8. ### Annihilation: calculation of photon energies

I set up this problem this way: ##p_a^{\mu}=(E, \sqrt{E^2-m^2}, 0, 0)## ##p_b^{\mu}=(m, 0, 0, 0)## ##p_c^{\mu}=(2E_\gamma, 2E_\gamma, 0, 0)## I have chosen to consider the two photons as a single particle of energy equal to ##2E_\gamma##. At this point I applied conservation of the...
9. ### Write the equations of a mass and spring in different accelerated systems

Hi I know that the equation of a simple harmonic oscillator is ##\ddot x + \omega^2 x=0##. The thing is that I don't know how to get to that equation in the situations given. In the first situation, I know that ##x) k(x-x_0)=m(\ddot x -x \dot \theta ^2)## ##y) N=m(2 \dot x \dot \theta)## So...
10. ### The average rate of energy loss resulting from internal friction

Summary:: Having the following dates:
11. ### Dynamics homework -- Motion of a stick attached to a rolling disk

Hi everyone, I need help for this homework. I'm a mechatronics engineering student and i want to solve this question but no matter how hard I try, I can't solve the question. Sorry for my bad english... The disk connected to the AB stick with a length of 2 meters is rolled as shown in the...
12. ### An object with mass m moving on x'x and Ep(x) = (1/2)*k*(x^2 - 4)^2

Hi ! This is my try: Is that correct ? Thanks

15. ### Find the force needed for a body on an inclined plane to be static?

Here, I have two doubts 1) if the surfaces are frictionless, then there's no force being applied on the ##x' axis## of ##m_1## except from the weight, so it should be sliding, shouldn't it? So, there's no force that I could apply to ##m_2## to keep ##m_1## in equilibrium since any force that I...
16. ### Man on ladder: jump off instantly vs last moment?

So there are two cases: a). free fall (straight forward for me) b). ladder rotating and jumping off in last moment (I am interested in trying to understand this case) I believe I should take into account momentum at the time the man hits the ground in both cases? The smaller, the better. Or...
17. ### Pitcher throwing a baseball

Hello. I have just started studying physics. Can someone explain to me how can I type in formulas here using Tex for nicer formatting? I suppose the force is F = ma. Question is: what is a? The starting throw angle is not mentioned, I suppose this task has to be related to gravity. All I know...
18. ### Force as a function of time

Hello, I have the force defined as a function of time, where F=A-Bt and A=100N, B=100Ns-1. I have to determine, how long it will take for object to stop, if t0=0s and v0=0,2ms-1 and mass of the object is m=10kg. Can somebody please help me with this, because I'm having hard time with this task.
19. ### A position of stable equilibrium, and the period of small oscillations

I tried by taking the derivative of the potential to find the critic points and the I took the second derivative to find which of those points are minimum points. I found that the point is ##x=- a##. I don't understand how to calculate the period, since I haven't seen anything about the harmonic...
20. ### Calculate the natural circular frequency ωn of the system

Homework Statement Calculate the natural circular frequency ωn of the system shown in the figure. The mass and friction of the pulleys are negligible. The diagram is attached. Homework Equations ωn = (k/m)1/2 The Attempt at a Solution I can see the total mass of the system is 3m. So in the...
21. ### Find the range of acceleration so that the drums won't fall

Problem: https://drive.google.com/open?id=19PDuyshgP6u4U9mXU3BfrF031J8wL12B Attempt: I tried to solve the range by listing out the Newton's 2nd laws of each drum https://drive.google.com/open?id=1Eslg2Wy3orG41eywwm_O6qN4OQ3QN-bA and from the equations of the drum 2, I get...
22. ### Hi, help me to check my answers, dynamics, energy and work

Homework Statement Whats is the final speed of the second box(mass = 1kg) when the first one (mass = 5 kg) has descended a distance equal to 0.6 meters in the rough ramp inclined 60° respect the x axis. Consider the spring is compressed a length x = 0.2 meters. The second box is tied to the...
23. ### The phase of a simple harmonic motion

Homework Statement How can I calculate the initial phase in a simple harmonic motion if I only have the amplitude, frequency and angular velocity as data? Homework Equations The formula of the position, in fact they ask me to do the formula that allows to know the elongation depending on the...
24. ### Which force creates the torque?

Homework Statement Homework Equations The Attempt at a Solution F12 is just an internal force caused by the joint 1 right? how can an internal force cause a torque?
25. ### Mass moment of inertia of an airplane about its main gear

Homework Statement Okay, so this isn't so much a problem as a design issue while following an example given in a book. (Relevant material is here: http://www.aero.us.es/adesign/Slides/Extra/Stability/Design_Control_Surface/Chapter%2012.%20Desig%20of%20Control%20Surfaces%20(Elevator).pdf ) Now...
26. ### Elastic collisions and Newton's third law

Hi everyone, I am new to this forum, and I'm having a hard time understanding Newton's third law and collisions, first of all I want to say that it is not homework and that I do know the basics of physics, vectors, energy, work, and momentum I also know and understand Newton's first and second...
27. ### What is the direction of P relative to A?

Homework Statement Homework Equations The Attempt at a Solution does Vpa has the same direction as Vp? i thought Vp is tangent to the circular path that point P creates( perpendicular to vector Rpa) but from the figure, Vp doesn't seem to be tangent to the path, but Vpa does...
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### Lifting a Beam with a uniform weight distribution

Homework Statement Hi There, I'm having trouble understanding (what I guess should be) a simple concept and so I can't apply it to a project I'm working on (also kind of rusty on torques and mechanics problems) If I have a hinged beam (of uniform weight) and I lift it from one end and stay...
29. K

### Dynamics of a point mass in circular motion

Homework Statement Dear All, I'm having a hard time solving the following problem: A point of mass is moving on a circular plane (Oxy), where the circle's formula is: The force acting on mass "m" is defined as: We're looking for velocity of point "m" in position (1,1) =V1, and in position...
30. J

### Draw a FBD, calculate tension in the string, determine mass

Homework Statement A box slides on a smooth (frictionless) horizontal surface, 1.50 m above the floor, at a speed of 2.00 m/s. The box then slides down a ramp that makes an angle of 36 deg with the horizontal and has a coefficient of kinetic friction equal to 0.430. After reaching the end of...
31. J

### A dinner plate, of mass 580 g is pushed .... find work/F

Homework Statement A dinner plate, of mass 580 g is pushed 90.0cm along a dining room table by a constant force of F = 3.60 N directed at angle theta = 24.0 deg below the horizontal. If the coefficient of kinetic friction between the plate and the table's surface is 0.440 determine a. the...
32. ### I Why use velocity dispersion in Faber Jackson relation

Hi all, Recently I am reading some online material about Tully-Fisher relation and Faber-Jackson relation which is describing the dynamical constrain on the mass of spiral/elliptical galaxies. In spiral galaxy, TF relation suggest Luminsoty ≈ (some const) (Vmax)^4 while in elliptical galaxy...
33. ### Normal force in a curvilnear motion

Homework Statement The system shown is initially at rest when the bent bar starts to rotate about the vertical axis AB with constant angular acceleration a 0 = 3 rad/ s2 . The coefficient of static friction between the collar of mass m = 2 kg and the bent bar is f.Ls = 0.35, and the collar is...
34. ### A car traveling upward on inclined plane

Homework Statement consider a 3300 lb car whose speed is increased by 35 mph over a distance of 200 ft while traveling up a rectilinear incline with a 15% grade. model the car as a particle, assume the tires do not slip, neglect all sources of frictional losses and drag. find the work done by...
35. ### Deflection in a Dynamic Shaft

I am curious how the deflection of a shaft changes due to rotation. In the force diagram image the green arrows show the rotational fixture locations and the purple arrow show the location of the applied force. The second image shows the deflection during a static test. If the force is applied...
36. ### Finding force of friction

Homework Statement Ok so there was a question on a physics quiz I did that I have no idea how to answer. There was a roller coaster going down a hill with an initial velocity of 1.67m/s. The hill is 60m long and had an angle of 40 degrees. There is a coefficient of friction of 0.100 with the...
37. ### Dynamics Questions // Elastic Collision with different Vo

Homework Statement [/B] A 2.3 kg object traveling at 6.1 m/s collides head-on with a 3.5 kg object traveling in the opposite direction at 4.8 m/s. If the collisions is perfectly elastic, what is the final speed of the 2.3 kg object? Homework Equations Conservation of Energy: 1/2 m*vi^2 = 1/2...
38. ### I Boom Crane - Lagrangian

Hi, I am trying to model the position of the suspended mass at the end on a boom crane. This is basically a spherical pendulum, however further complicated by the fact that the mass can be hoisted up and down and also the pivot is connected to an arm (boom) which can be rotated up and down and...
39. ### The Acceleration of a Sliding Collar on a Shaft

Homework Statement For the mechanism shown, determine the speed and magnitude of the acceleration of collar C in terms of b, θ, θ-dot, and θ-dot-dot. Check the attached file for the diagram. We are given the length b and angle θ. Homework Equations ΣF=ma The Attempt at a Solution I...
40. ### Superman's skid marks?

Homework Statement So here is the Problem: A big truck (m=50t) is going at 100km/h. Now the truck can't brake anymore and Superman comes to aid. He (has a mass of m=100kg) tries to stop the truck while he is wearing shoes with a rubber-texture and a friction coefficient of µ = 0.8. Assume that...
41. ### Blobbing - energy loss

Homework Statement Blobbing is one of the extreme attractions in aquaparks. A person is lying on a big raft positioned on the surface of water and filled with low-pressured air. Another person jumps down from a given height onto the opposite end of that raft, throwing the lying person in the...
42. ### Droop control (load sharing in AC Mains distribution networks)

Hi, I have quite a superficial understanding of Droop control: http://www.openelectrical.org/wiki/index.php?title=Droop_Control https://en.wikipedia.org/wiki/Droop_speed_control I'm not after a super technically detailed explanation, but if anyone has any more detailed sources for how it is...
43. ### I would like to know what the dynamic force load is....

Homework Statement I am currently doing an internship and as part of my assignemnt I have to calculate the dynamic load on the bearing of a certain part that is rotating about a fixed point. https://www.physicsforums.com/attachments/chute-png.103400/ [Broken] This is the part that moves ( the...
44. ### Verify Sol. of an Dynamic Problem with 2 Wheels

1. The problem is the following: Starting from stillness @ t = 0, we are looking for the acceleration @T=0 of the 2 wheels (rolling without slip, in particular in point P4 we have a gear wheel contact so we can have that the reaction R2y of the plane could be also in direction y2, in this case...
45. ### Minimum Vo for a hoop to get to the top

Homework Statement part(b) and (c) Homework Equations Conservation of momentum Conservation of angular momentum Conservation of mechanical energy The Attempt at a Solution So first I thought that I could do it by just using the conservation of mechanical energy, but then I realized that since...
46. ### Equations that define a human fall forward

Ok so what I want to create is a simulation of how the acceleration of a person falling would change according to the person's mass and height. This would then be explored in Matlab. Therefore, first, I am trying to find out the equations that would relate acceleration motion with mass and...
47. ### Dynamic problem with pulley

Homework Statement You have a a mass, m1, in a plane. This mass is connected to a pulley by a thread, to a mass m2. Prove that: \begin{equation} m_{1} = \dfrac{m_{2}(2g - a)}{4a} \end{equation} Homework Equations The Attempt at a Solution I don't know why, but I can get this...
48. ### Find the frequency of the cylinder's vertical vibration

Homework Statement Homework Equations w = √k/m w = 2π/P ƒ = 1/P The Attempt at a Solution I feel like I'm so close to the answer, I think it has something to do with the fact that there's a spring and pulley in the system that is throwing my answer off. I have √k/m = 2π/P So, P =...
49. ### Concrete Block Incline acceleration question

Homework Statement A concrete block of mass 25kg is placed on a smooth slope that makes an angle of 30 degrees with the horizontal. Ignoring the effects of air resistance, calculate a) the acceleration of the block as it slides down (g = 9.81 ms-2) b) the distance the block moves in 3 seconds...
50. ### Tension of a pendulum and force components

Homework Statement What is the tension in a pendulum? Is T=mgcos(theta) or is T=mg/(cos(theta)) ? and is the x component of tension is mgsin(theta) and this is the restoring force? Homework Equations Fnet=ma Fg=mg The Attempt at a Solution Maybe it depends on the problem given? But I am...