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Gravity Continued and Waves. Chapters 9, 11.1, and 11.2. Reminders. Lab A7-CE : Conservation of Energy due by Friday at 4pm Weekly Reflection #9 sent out later today. In-class Quiz #5 will take place next Thursday. Reading quiz due prior to class on Tuesday.
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Gravity Continued and Waves Chapters 9, 11.1, and 11.2
Reminders • Lab A7-CE: Conservation of Energydue by Friday at 4pm • Weekly Reflection #9 sent out later today. • In-class Quiz #5 will take place next Thursday. • Reading quiz due prior to class on Tuesday. • Optional extra credit review today. • Optional car crash reconstruction problem will be described after class as early as today.
Orbital Motion (Fg = Fc) In orbital motion, Fg = Fc, hence
Examples • Force between two objects: • Orbital velocity: • Escape velocity: • G = 6.67x10-11Nm2/kg2 • M = 5.97x1024kg • r = 6,371,000m
Key Concepts Chapter 11, Sec 1-2 • Simple Harmonic Oscillator • Terms: frequency (f), period (T), wavelength (λ), amplitude (A); note f = 1/T • Wave forms: • Longitudinal • Transverse • Polarization • d = vt implies v = λf
Extra Credit Review - Energy • A bullet is shot upward from with an initial speed of 55m/s. How high does it go? • #1: Use kinematics (equations of accelerated motion) to solve the problem. (1/2 point) • #2: Use conservation of energy to solve the problem. (1/2 point) • A 0.005kg bullet moving horizontally with a speed of 330m/s hits a wooden block with a mass of 2.3kg that is suspended like a pendulum but with two strings. The bullet become imbedded in the wood. • #3: What is the speed of the block right after the bullet is embedded in it? (1/2 point) • #4: How high does block & bullet go? (1/2 pt)
Extra Credit Review - Gravity • #1 Calculate the weight of a 0.454kg loaf of bread on the surface of Earth. Give the magnitude and direction of that force. • #2 Show that the local value of “g” (the gravitational field strength) on the surface of the moon is approximately 1/6 that on the surface of Earth. Note that gEarth= -9.81N/kg • #3 How much gravitational force exists between two 1kg lead spheres whose centers are 1m apart from one another? • #4 Show mathematically that the acceleration due to gravity in a 300km high orbit is 91.2% that on the surface of Earth. Assume a radius of 6,371km for Earth.
Car Crash Reconstruction Pointers 1 • Take your time and do it right. • Consider this a 2-phase crash: • For collision, use conservation of momentum. • Post collision, use conservation of energy, F=μN, and kinematics as necessary. • Make use of FΔt=mΔv, FΔd=ΔE, and ΣF=ma as necessary. • Treat N-S and E-W components separately. • Car #1 going due east; car #2 going due north. • Include body masses in calculations. • Develop a detailed drawing defining variables. • Work in metric units only; easy conversion via Internet – search “convert meters to feet”.
Car Crash Reconstruction Pointers 2 • Watch your units carefully. • Watch your subscripts carefully. • Might use a tiny bit of trigonometry, but not needed. • Work in teams to maximum effect. • Due last regular day of class (May 1). • Hard copy only; do not submit electronic files. • No group or “identical” reports will be accepted. • Will be scored “harshly” due to implications of making errors. Partial credit will be possible. • A rubric is provided and used to score the submission.