A mass m = 2.67 kg is attached to a spring of force constant k = 50.9 N/m and se
ID: 2263940 • Letter: A
Question
A mass m = 2.67 kg is attached to a spring of force constant k = 50.9 N/m and set into oscillation on a horizontal frictionless surface by stretching It en amount A = 0.15 m from its equilibrium position and then releasing it. The figure below shows the oscillating mass and the particle on the associated reference circle at some time after its release. The reference circle has a radius A, and the particle traveling on the reference circle has a constant counterclockwise angular speed omega, constant tangential speed V = omega A, and centripetal acceleration of constant magnitude ac = omega 2A. Determine the following. maximum speed of the oscillating mass m/s magnitude of the maximum acceleration of the oscillating mass m/s2 magnitude of the maximum force experienced by the oscillating mass N maximum kinetic energy of the oscillating mass J maximum elastic potential energy of the spring attached to the mass J total energy of the oscillating mass-spring system J If the record of time starts when x = +A and v = 0, determine expressions for the displacement, velocity, and acceleration of the oscillating mass along the x-axis at any time t later (Your expression should be in terms of the variableExplanation / Answer
omega = (k/m)^0.5 = sqrt(19.063) = 4.36
initial potential energy stored in the system when the spring is sreched by 0.15 m
= 1/2*k*0.15^2 = 0.57 J
by consrvation of energy
this potential energy will be converted nto kinetic energy at equillibrium position where it will have maximum kintic enrgy
and hence maximum velocity
so
0.57 = 1/2*2.67*v^2
v = 0.65 m/s
maximum speed = 0.65 m/s
acceleration = w^2 *displacement
maximum acceleration = w^2 *A as A is the maximum displacement
maximum acceleration = 19.063* 0.15 = 2.85 m/s^2
maxmum force will be exerted when maximum acceleration is taking place
maximum force = 2.67*2.85 = 7.63 N
maximum kinretic energy has already been found as 0.57 J
similarly maximum potential energy = 0.57 J
total energy of oscillation is same as maximum kinetic energy by conservation of enrgy principle
so its also 0.57J
at t= 0
displacement = A
the functon defining equation of positon be A cos(w*t+phi) since it is simple harmonic motion it can be eigther sin or cos function any function will be correct
so we have chosen cos function
A is the maximum displacement because it is initial displacement
x(t) = Acos(wt+phi)
at t= 0
A = Acos(phi)
cos(phi) = 1
phi = 0
At t = 0
v(t ) = 0
v(t) =w A sin(wt)
0 = w*A sin(0)
lhs = rhs so our equation is correct
x(t) = A *cos(4.36*t)
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