Lecture9

# Lecture9 - Homework#2 due no later than Friday February 3...

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Homework #2 due no later than Friday, February 3, 5:00 pm. Answers to Homework #1 are now posted on the Homework page of the class website

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The Doppler Shift: A shift in wavelength due to a wave emitter moving towards (shorter wavelength) or away (longer wavelength) from an observer. ∆λ v λ c = c known ∆λ measured v calculated
Measuring Radial Velocity We can measure the Doppler shift of emission or absorption lines in the spectrum of an astronomical object. We can then calculate the velocity of the object in the direction either towards or away from Earth. ( radial velocity ) ∆λ v λ c = known observed

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The Doppler Effect Light waves coming from an object moving towards you will have their wavelength shortened. Light waves coming from an object moving away from you will have their wavelength lengthened. Light waves from an object moving perpendicular to your line-of-sight will not change their wavelength. BLUESHIFT BLUESHIFT REDSHIFT REDSHIFT
Measuring Rotational Velocity

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Measuring Rotational Velocity (2)
Universal Laws of Motion Forces and Newton’s Laws of Motion

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Scalar : a quantity described solely by its size (and units) Vector : a quantity described by its size AND direction
speed – rate at which an object moves [m/s; mi/hr]. A scalar quantity. velocity – an object’s speed AND direction, e.g. “10 m/s moving east”. A vector quantity. acceleration – a change in an object’s velocity, i.e., a change in speed or direction [m/s 2 ]. A vector quantity.

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Forces change the motion of objects. This “acceleration” can be a change in speed OR in the direction of motion OR both
The Acceleration of Gravity As objects fall, they accelerate. The acceleration due to Earth’s gravity is 9.8 m/s each second, or g = 9.8 m/s 2 . The higher you drop the ball, the greater its velocity will be at impact.

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Galileo demonstrated that g is the same for all objects, regardless of their mass!
Momentum (p) – the mass of an object times its velocity (p=mv) Force (f) – anything that can cause a change in an object’s momentum As long as the object’s mass does not change, the force

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Lecture9 - Homework#2 due no later than Friday February 3...

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