Textbook Notes (363,260)
Astronomy (66)
AST201H5 (14)
J B Lester (10)
Chapter 4

# summary_ch4.pdf

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School
University of Toronto Mississauga
Department
Astronomy
Course
AST201H5
Professor
J B Lester
Semester
Fall

Description
AST 201S - Stars and Galaxies University of Toronto Mississauga Chapter 4 Summary th Essential Cosmic Evolution, 5 Edition 1. Precise deﬁnitions of terms relating to motion: • speed = change of location/position in an amount of time - m/s • velocity = change of location/position in a particular direction in an amount of time - m/s • acceleration = change in velocity in an amount of time - m/s/s or m/s 2 • momentum = mass × velocity - has direction • net force = sum of all force aﬀecting an object 2. Mass = amount of matter in a body 3. Weight = force of gravity on the mass of an object 4. Newton’s laws of motion. (a) 1 Law: If there is no net force, the momentum remains constant - same speed and same direction (b) 2nd Law: If there is a net force, the momentum changes - either the speed changes or the direction changes or both the speed and direction change rd (c) 3 Law: For every force there is an equal and opposite reaction force 5. Newton’s law of gravity (a) F g G M1×2 2 d (b) Note: F gepends directly on both masses multiplied together (c) Note: F gepends inversely on separation squared (d) Because mass is always positive, there is never a cancellation, as can happen with + and − electric charges or N and S magnetic poles (e) As the separation increases the force of gravity weakens, but never goes to zero if the separation is less than inﬁnity (f) Gravity is extremely
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