* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Problems for Mathematics of Motion: week 6
Relational approach to quantum physics wikipedia , lookup
Eigenstate thermalization hypothesis wikipedia , lookup
Velocity-addition formula wikipedia , lookup
Tensor operator wikipedia , lookup
Photon polarization wikipedia , lookup
Path integral formulation wikipedia , lookup
Atomic theory wikipedia , lookup
Symmetry in quantum mechanics wikipedia , lookup
Old quantum theory wikipedia , lookup
Angular momentum operator wikipedia , lookup
Routhian mechanics wikipedia , lookup
Monte Carlo methods for electron transport wikipedia , lookup
Lagrangian mechanics wikipedia , lookup
Four-vector wikipedia , lookup
Particle filter wikipedia , lookup
Mean field particle methods wikipedia , lookup
Elementary particle wikipedia , lookup
Hunting oscillation wikipedia , lookup
Relativistic mechanics wikipedia , lookup
Seismometer wikipedia , lookup
Newton's laws of motion wikipedia , lookup
Laplace–Runge–Lenz vector wikipedia , lookup
Classical mechanics wikipedia , lookup
Rigid body dynamics wikipedia , lookup
Relativistic quantum mechanics wikipedia , lookup
Relativistic angular momentum wikipedia , lookup
Brownian motion wikipedia , lookup
Equations of motion wikipedia , lookup
Centripetal force wikipedia , lookup
Newton's theorem of revolving orbits wikipedia , lookup
Theoretical and experimental justification for the Schrödinger equation wikipedia , lookup
Problems for Mathematics of Motion: week 6 Module F12MR2 2006-07 Important: Questions 1 and 2 on this sheet (with changed numerical values) will constitute the second test for this module. This test will take place on Monday 19 February. You do not need to hand in group solutions for these questions. Question 3 should be discussed in the groups, and handed in as usual before the class on Monday 19 February. 1 At time t seconds, a particle of mass m = 1 kg has position vector ~r(t) metres relative to some ~r fixed origin O. The particle moves under the influence of a central force F~ = −4 3 Newtons. r (a) Write down the equation of motion for the particle’s position. 1 4 (b) Show that the total energy E = ~r˙ ·~r˙ − is conserved during the motion. 2 r ~ = ~r × ~r˙ is conserved during the motion. (c) Show that the total angular momentum L (d) If the particle’s initial position is ~r(0) = ~i metres and its initial velocity ~r˙ (0) = 2~j m/s, ~ Show that the motion takes place in the ~i~j-plane. compute E and L. (e) In terms of polar coordinates (r, θ) in the ~i, ~j-plane the position vector can be written ~r = r cos θ ~i + r sin θ ~j where both r and θ are functions of t. Show that the angular ~ = r2 θ̇~k and that 1 ~r˙ ·~r˙ = 1 (ṙ2 + r2 θ̇2 ). momentum can be expressed as L 2 2 4 1 2 L2 (f) Use the results of (e) to derive the formula E = ṙ + 2 − for the total energy (L = 2 2r r ~ |L|). Insert the values for E and L found in (d) to obtain a differential equation for r. 2 At time t seconds, a particle of mass m kg has position vector ~r(t) metres relative to some fixed origin O. The particle moves under the influence of the force F~ = 4~r˙ × ~k Newtons, where ~k is a constant unit vector. (a) Write down the equation of motion for the particle’s position. (b) Show that kinetic energy E = 1 m~r˙ ·~r˙ is conserved during the motion. 2 (c) Suppose that the particle’s mass is m = 1 kg, its initial position is given by ~r(0) = 4~i and its initial velocity is ~r˙ (0) = −16~j + ~k. Show that the equation of motion and the initial conditions are satisfied by ~r(t) = R cos(ωt)~i + R sin(ωt)~j + vt~k, where R, ω, v are constants which you should determine. continued overleaf 1 (1) 3 A particle of mass m = 1 kg moves under a central force of attraction fixed point O where r is the distance from O and α is a constant. α r2 directed towards a (a) In the lecture we showed that the orbit of the particle is an ellipse if the total energy E is negative. If L is the magnitude of the angular momentum about O express the semi-latus rectum ` and eccentricity of the ellipse in terms of α, E and L . (b) Use energy to show that the particle’s speed v is related to the distance r by conservation 2 α 2 v2 = m + `−1 . r (c) If the of the particle is a circle with centre O and radius a, show that its speed is ppath α u = ma . (d) Assuming that the orbit is an ellipse with semi-major axis a and semi-minor axis b show . that the period of the motion is given by T = 2πabm L 2 (e) In the case of an earth satellite for which O is the q centre of the earth and α = mgR where R is the radius of the earth show that T = 2π R a3 . g (f) A satellite has maximum and minimum heights of 750km and 250km respectively, above the surface of the earth. Find the period of revolution. (Radius of the earth = 6400km, g = 9.81ms−2 ). 2