Simple Harmonic Motion - Acceleration, position, velocity Contents: Kinematics

Simple Harmonic Motion - Definition motion: F = -kx A Mass on a Spring (Demo) TOC

x o = Maximum displacement (AKA Amplitude) v o = (  x o ) = Maximum velocity a o = Maximum acceleration TOC x: -x o 0 +x o v: 0 + /- v o 0 a: +a o 0 -a o Show – Logger Pro SHM Show – ip SHM ROT

Simple Harmonic Motion - Kinematics  = 2  T = 1  = 2  f T f a = -  2 x x = x o sin(  t) or x o cos(  t) v =  x o cos(  t) or -  x o sin(  t) TOC  – “Angular” velocity T – Period of motion x – Position (at some time) v – Velocity (at some time) Show x o – Max Position (Amplitude) v o – Max Velocity (in terms of  and x o )

Example: (Are you in RADIANS????) A SHO goes up and down, and has a period of 12 seconds, and an amplitude of 5.0 m. If it starts in the middle going upward: a) What is its position in 6.5 seconds? (7.0 s, x = ???) b) What is its velocity in 6.5 seconds? c) What times will it be at the top? d) When will it be at the bottom? e) What is its velocity when it is at a position of 1.75 m? TOC  = 2  /12, x o = 5.0 a) use x = x o sin(  t), x = …m v o = max, so x = 0, so v o =   ( x o 2 ) =  x o = …m/s b) use v = v o cos(  t), v o = …m/s, v = m/s c) ¼ of a period – 3.0 sec, then 15.0, then 27.0, … d) ¾ of a period – 9.0 sec, then 21.0 sec, then 33.0 sec, … e) use v = +   ( x o 2 - x 2 ), v = … m/s

Whiteboards: Kinematics 11 | 2 | 3 | 4 | 523 TOC

What is the period of a guitar string that is vibrating 156 times a second? (156 Hz) Use f = 1/T s W

An SHO has a period of s. What is its frequency? Use f = 1/T 4.44 Hz W

A mass on the end of a spring oscillates with a period of 2.52 seconds and an amplitude of m. What is its maximum velocity? (save this value) v = +   ( x o 2 - x 2 ), make x = 0,  = 2  /2.52, |v| = …. m/s 1.12 m/s W

A mass on the end of a spring oscillates with a period of 2.52 seconds and an amplitude of m. (assuming it starts at x = 0, moving upwards.) a) write an equation for its position b) write an equation for its velocity v o = 1.12 m/s x o = m  = 2  /2.52 = 2.49 rad/s x = 0.450sin(2.49t) v = 1.12cos(2.49t) 1.1 m/s W

A SHO has an equation of motion of: (in m) x = 2.4sin(6.1t) a) what is the amplitude and angular velocity of the oscillator? b) what is its period? c) what is its maximum velocity? d) write an equation for its velocity. x o = 2.4 m,  = 6.1 rad/s T = 2  /6.1 = 1.03 s v o = (6.1 rad/s)(2.4 m) = v = 15cos(6.1t) 2.4 m – 6.1 rad/s 1.0 s 15 m/s v = 15cos(6.1t) W

A mass on the end of a spring oscillates with a period of 2.52 seconds and an amplitude of 0.45 m. What is its velocity when it is 0.37 m from equilibrium? v = +   ( x o 2 - x 2 ), make x = 0.37,  = 2  /2.52, v = …. m/s +.64 m/s W

A loudspeaker makes a pure tone at Hz. If it moves with an amplitude of 0.87 cm, what is its maximum velocity? (0.87 cm =.0087 m) (f = 1/T) v = +   ( x o 2 - x 2 ), make x = 0,  = 2  (440), |v| = …. m/s 24 m/s W

A mass on the end of a spring oscillates with a period of 1.12 seconds and an amplitude of 0.15 m. Suppose it is moving upward and is at equilibrium at t = 0. What is its position at t = 13.5 s? use x = x o sin(  t),  = 2  /1.12, x o = 0.15, x = …m m W

A mass on the end of a spring oscillates with a period of 1.12 seconds and an amplitude of 0.15 m. Suppose it is moving upward and is at equilibrium at t = 0. What is its velocity at t = 13.5 s? use v = v o cos(  t),  = 2  /1.12, v o =   ( x o 2 ) =  x o, v = … m/s m/s W