Chapter 7, Problem 7.21P

A body of mass m is suspended by a rod of length L that pivots without friction (as shown). The mass is slowly lifted along a circular arc to a height h. a. Assuming the only force acting on the mass is the gravitational force, show that the component of this force acting along the arc of motion is F = mg sin u. b. Noting that an element of length along the path of the pendulum is ds = L du, evaluate an integral in u to show that the work done in lifting the mass to a height h is mgh.

Consider a particle moving in uniform circular motion in the xy plane at a distance r = 1.1 m from the origin. Refer to the figure. In this problem, you will show that the projection of the particle’s motion onto the x-­axis can be used to represent simple harmonic motion. a. If the particle moves counterclockwise at a constant angular velocity of ω, and at time t = 0 its coordinates are (x,y) = (r,0), enter an expression for the projection of the particle’s position onto the x-axis, in terms of r, ω, and t.  b.  For an angular speed of ω = 7.4 rad/s, find the value of x, in meters, at time t = 0.44 s.  c.  Considering the expression you entered in part (a) for the projection of the particle’s position onto the x-axis, can the projection’s motion be described as simple harmonic motion?   d. Which of the graphs correctly shows the projection of the position of the moving particle onto the x-axis as a function of t for two full cycles?   e.  Enter an expression for the velocity function,…

The one-dimensional harmonic oscillator has the Lagrangian L = mx˙2 − kx2/2. Suppose you did not know the solution of the motion, but realized that the motion must be periodic and therefore could be described by a Fourier series of the form x(t) =∑j=0 aj cos jωt, (taking t = 0 at a turning point) where ω is the (unknown) angular frequency of the motion. This representation for x(t) defines many_parameter path for the system point in configuration space. Consider the action integral I for two points t1 and t2 separated by the period T = 2π/ω. Show that with this form for the system path, I is an extremum for nonvanishing x only if aj = 0, for j ≠ 1, and only if ω2 = k/m.

Let the initial position and speed of an overdamped, nondriven oscillator be x0 and v0, respectively. (a) Show that the values of the amplitudes A1 and A2 in Equation 3.44 have the values A1=2x0+v021 and A2=1x0+v021 where 1 = 2 and 2 = + 2. (b) Show that when A1 = 0, the phase paths of Figure 3-11 must be along the dashed curve given by x=2x, otherwise the asymptotic paths are along the other dashed curve given by x=1x. Hint: Note that 2 1 and find the asymptotic paths when t .

Find g at a point on earth where T=2.01 s for a simple pendeulum of length 1.00 m, undergoing small-amplitude-oscillations.

Let's consider a simple pendulum, consisting of a point mass m, fixed to the end of a massless rod of length l, whose other end is fixed so that the mass can swing freely in a vertical plane. The pendulum's position can be specified by its angle Φ from the equilbrium position. Prove that the pendulum's potential energy is U(ϕ)=mgl(1−cosϕ). Write down the total energy E as a function of Φ and ϕ˙. Show that by differentiating E with respect to t you can get the equation of motion for Φ. Solve for Φ(t). If you solve properly, you should find periodic motion. What is the period of the motion?

A point mass is constrained to move on a massless hoop of radius a fixedin a vertical plane that rotates about its vertical symmetry axis with constantangular speed ω. Obtain the Lagrange equations of motion assuming the only external forces arise from gravity. What are the constants of motion? Show that if ω is greater than a critical value ω0, there can be a solution in which the particle remains stationary on the hoop at a point other than at thebottom, but that if ω < ω0, the only stationary point for the particle is atthe bottom of the hoop. What is the value of ω0?

Two springs of force constants k1 and k2 are attached to a block of mass m and to fixed supports as shown in Fig. 2. The table surface is frictionless. (a)  If the block is displaced from its equilibrium position and is then released, show that its motion will be simple harmonic with angular frequency w = √(k1 + k2)/m. (b)  Suppose the system is now submersed in a liquid with damping coefficient b , what is the condition that the block will return to itsequilibrium position without oscillation?Sketch a graph to show the behavior of the system in this case.