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Classical Mechanics Unit 13 Examples Unit 14 Concepts. Today’s Examples: a) Elastic collisions… b) Impulse, Force during collisions . Today’s Concepts: a) Rotational Motion b) Moment of Inertia. Main Points. Main Points. Main Points. Kinetic Energy of the System.
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Classical MechanicsUnit 13 Examples Unit 14 Concepts • Today’s Examples: • a) Elastic collisions… • b) Impulse, Force during collisions Today’s Concepts: a) Rotational Motion b) Moment of Inertia
DP=pf-pi pi q Another way to look at it: -pi pf q pf |p|=mv |DPX | = 2mv cosq |DPY| = 0
pi Another way to look at it: pf DP = pf-pi pf -pi Favg = DP/Dt |DP| = |pf–pi| = m|vf–vi| Dt = DP/Favg
Ball Hits Wall 2 |p|=mv
Ball Hits Wall 2 |DPX | = 2mv cosq |DPY| = 0 Dt = DP/Favg
Ball Hits Wall 2 DP = pf-pi pf -pi |DP| = |pf–pi| = m|vf–vi|
Ball Hits Wall 2 Favg = DP/Dt
Classical MechanicsUnit 14 Concepts Today’s Concepts: a) Rotational Motion b) Moment of Inertia
Linear Dynamics Describes motion of point particles (or center of mass)…
Rotational Kinematics Needed to fully describe motion of systems of particles…or extended objects Motion relative to center of mass
Summary of Rotations Angular velocity w is measured in radians/sec Frequency f is measured in revolutions/sec 1 revolution =2p radians PeriodT = 1/f
Another Summary w Constant a does not mean constant w
Clicker Question A disk spins at 2 revolutions/sec. What is its period? A) T= 2 sec B)T= 2p sec C) T=½ sec
Clicker Question A disk spins at 2 revolutions/sec. What is its angular velocity? A) B) C) rad/sec rad/sec rad/sec
CheckPoint a A wheel which is initially at rest starts to turn with a constant angular acceleration. After 4 seconds it has made 4 complete revolutions. How many revolutions has it made after 8 seconds? A) 8 B) 12 C) 16 Everyone got this right!!!
CheckPoint Response a After 4 seconds it has made 4 complete revolutions. How many revolutions has it made after 8 seconds? A) 8 B) 12 C) 16 C) The number of revolutions is proportional to time squared.