Twin spring system with a mass in between (X and Y direction)

AI Thread Summary
The discussion revolves around modeling the motion of a mass between two coupled springs in both X and Y directions after an impulse is applied. The user is seeking guidance on starting a simulation project in Excel, focusing on drawing a Free Body Diagram (FBD) and calculating forces. Key points include the need to establish the equilibrium position, understand the forces acting on the mass, and determine appropriate time steps for the simulation. The user is also exploring the relationships between spring constants, mass, and angles, realizing that these parameters must be proportionate. The conversation emphasizes the importance of accurately calculating forces and setting up the simulation framework.
  • #51
If the mass moves 1 unit of length in the +x direction, what is the change in ##L_1## ? And in ##L_2## ? This has consequences for ##F_1, F_{1,x}, F_{1,y}, \theta_1, F_2, F_{2,x}, F_{2,y}, F_{tot, x}, F_{tot, y}, \theta_2 ## so also for ##a_x, a_y##

[edit] and ##\sin\theta_1 = h/L_1 \quad \Rightarrow \quad \theta_1 = \arcsin (h/L_1) ##, etc !
 
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  • #52
The simulation you are setting up will integrate the equations of motion, ##\vec {\bf a} = \vec {\bf F} / m##

At ##t_0 = 0## you have $$ x_0 = 0, \\ y_0= 0, \\ v_{x,0} = ..., \\ v_{y,0} = ... , \\ a_{x,0} = 0, \\ a_{y,0} = 0
$$With the simplest integrator, forward Euler, you can calculate the situation
at t = ##t_0 + \Delta t ##:$$ x = x_0 + v_{x_0} \Delta t , \\ y = y_0 + v_{y,0} \Delta t, \\ v_{x} = v_{x_0} + a_{x,0} \Delta t \\
v_{y} = v_{y_0} + a_{y,0} \Delta t
$$ and then you need to calculate a new ##\vec {\bf a} ## at position ##\left (x(\Delta_t), y(\Delta_t) \right ) ##
and so on.
 
  • #53
BvU said:
The simulation you are setting up will integrate the equations of motion, ##\vec {\bf a} = \vec {\bf F} / m##

For some reason i cannot reply your equation without the site going nuts.

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Thanks for those equations. THIS ONE, : X = X0 + V0 * ΔT, Shouldtn it be, Xn = Xn-1 + Vn * ΔT ?
With n the current timestep
So the current speed instead of the previous speed?

and for the acceleration:, an+1 = Fn+1/m
 
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  • #54
MrNewton said:
Thanks for those equations. THIS ONE, : X = X0 + V0 * ΔT, Shouldtn it be, Xn = Xn-1 + Vn * ΔT ?
With n the current timestep
So the current speed instead of the previous speed?

and for the acceleration:, an+1 = Fn+1/m
The starting point is the position and velocity, ##\vec r_0##, ##\dot{\vec r}_0##.
From these you calculate an acceleration, ##\ddot {\vec r}_0##.
For the next timestep, ##\dot {\vec r}_1=\dot{\vec r}_0+\ddot {\vec r}_0\Delta t##.
So for calculating ##\vec r_1## you have two velocities available. Taking the average should work well.
 
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