Consider a mass m suspended by a spring of stiffness k and damper of coefficient c, arranged in parallel with each other as illustrated in Figure Q2. The mass is initially pulled downwards, in a direction termed positive-x, by a forcing function F F, cos wt. After a short period of time steady-state behaviour, characterised by a lag between force and displacement of o radians, comes to predominate. The maximum displacement described by this motion has a magnitude of X. The system is in a resonant state. Q2 k F = F,cos(wt) %3D Figure Q2 Write equations for the displacement x, velocity x, and acceleration i of the mass, using cosine terms. (a) Thus, given that the overall equation of motion is Fo cos(wt) - mä – cx – kx = (b) 0, express the terms of the equation using a vector diagram. Identify the angles ot and , and ensure that the angles you draw are labelled (where appropriate) with values that are compatible with the state of the system described in the question above. This is to be a professional-quality engineering sketch. E

Elements Of Electromagnetics
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Consider a mass m suspended by a spring of stiffness k and damper of
coefficient c, arranged in parallel with each other as illustrated in Figure Q2.
The mass is initially pulled downwards, in a direction termed positive-x, by a
forcing function F = F, cos wt. After a short period of time steady-state
behaviour, characterised by a lag between force and displacement of 6 radians,
comes to predominate. The maximum displacement described by this motion
has a magnitude of X. The system is in a resonant state.
Q2
k
m
F = F,cos(wt)
Figure Q2
Write equations for the displacement x, velocity x, and acceleration i of the
mass, using cosine terms.
(a)
Thus, given that the overall equation of motion is Fo cos(wt) – mä – ci -
kx = 0, express the terms of the equation using a vector diagram. Identify the
angles ot and o, and ensure that the angles you draw are labelled (where
appropriate) with values that are compatible with the state of the system
described in the question above. This is to be a professional-quality engineering
sketch.
(b)
Rearrange this diagram into a vector polygon, again to a professional quality,
and use this polygon to extract X/F, in terms of k, 5, and B. Characterise the
transmitted force you expect to see, given the state of the system.
(c)
(d)
Imagine that Fo is set to zero, and the attachment point is instead displaced,
sinusoidally, in a new vertical co-ordinate y. Using a value of X/F. derived from
your vector polygon, show that adjustments to the value of B could make the
displacement x a function of either y or y.
Discuss the two devices you have modelled in part (d). What are their names,
what do they measure, and what size are they?
(e)
Transcribed Image Text:Consider a mass m suspended by a spring of stiffness k and damper of coefficient c, arranged in parallel with each other as illustrated in Figure Q2. The mass is initially pulled downwards, in a direction termed positive-x, by a forcing function F = F, cos wt. After a short period of time steady-state behaviour, characterised by a lag between force and displacement of 6 radians, comes to predominate. The maximum displacement described by this motion has a magnitude of X. The system is in a resonant state. Q2 k m F = F,cos(wt) Figure Q2 Write equations for the displacement x, velocity x, and acceleration i of the mass, using cosine terms. (a) Thus, given that the overall equation of motion is Fo cos(wt) – mä – ci - kx = 0, express the terms of the equation using a vector diagram. Identify the angles ot and o, and ensure that the angles you draw are labelled (where appropriate) with values that are compatible with the state of the system described in the question above. This is to be a professional-quality engineering sketch. (b) Rearrange this diagram into a vector polygon, again to a professional quality, and use this polygon to extract X/F, in terms of k, 5, and B. Characterise the transmitted force you expect to see, given the state of the system. (c) (d) Imagine that Fo is set to zero, and the attachment point is instead displaced, sinusoidally, in a new vertical co-ordinate y. Using a value of X/F. derived from your vector polygon, show that adjustments to the value of B could make the displacement x a function of either y or y. Discuss the two devices you have modelled in part (d). What are their names, what do they measure, and what size are they? (e)
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