Derive the equation of motion of the spring-mass system given below. Please show and MARK your derivation step by step. Missing
steps will result in losing points. Use the assumptions sin(θ) = θ and cos(θ) = 1.
1 answer:
Answer:
Ö + θ ( (k/m) + (g/l)) = 0
Step-by-step explanation:
Use the FBD attached:
Apply Newtons 2 nd Law in tangential direction:
Sum ( Ft ) = m*a
Sum of all tangential forces is:
m*g*sin(θ) + k*l*sin(θ)*cos(θ) = - m*l*Ö
Using small angle approximations:
sin (θ) = θ
cos (θ) = 1
Ö = angular acceleration.
m*g*θ + k*l*θ = -m*l*Ö
Ö + θ ( (k/m) + (g/l)) = 0
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Divide through everything by <em>b</em> :
Since <em>a/b</em> < <em>c/d</em>, it follows that
Multiply through everything on the right side by <em>b/d</em> to get
and so (<em>a</em> + <em>c</em>)/(<em>b</em> + <em>d</em>) < <em>c/d</em>.
For the other side, you can do something similar and divide through everything by <em>d</em> :
and <em>a/b</em> < <em>c/d</em> tells us that
Then
and so (<em>a</em> + <em>c</em>)/(<em>b</em> + <em>d</em>) > <em>a/b</em>.
Then together we get the desired inequality.