ASTR 1 Lecture Notes - Lecture 6: Weightlessness, Net Force, Vis Viva
12 Jun 2018
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Galaxy Formation: A Journey Through Cosmic Time
How do we describe motion?
Precise definitions to describe motion:
- Speed: Rate at which objects move
- speed=distance/time (units of m/s)
- Velocity: Speed and direction
- Acceleration: Rate of change in velocity - units of speed/time (m/s^2)
The Acceleration of Gravity
- All falling objects at the same rate (not counting friction of air resistance).
- On Earth, g=10 m/s^2: Speed increases 10 m/s with each second of falling.
- Gravity does not affect horizontal velocity
- Acceleration of Gravity: Downward velocity increases by about 10 m/s with each passing
second
Momentum and Force
- Momentum= mass x velocity
- A net force changes momentum, which generally means an acceleration (change in
velocity)
- A force is something that we can “feel”
- Rotational momentum of a spinning
How is mass different from weight?
- Mass - The amount of matter in an object
- Weight - The force that acts upon an object
- You are weightless in freefall
Why are astronauts weightless in space?
- There is gravity in space
- Weightlessness is due to a constant state of freefall
Newton’s Laws of Motion
- How did Newton change our view of the universe?
- Realized the same physical laws that operate in Earth also operate in the
heavens
- One universe
What are newton’s 3 laws of motion
- Newton's first law of motion - An object moves at a constant velocity unless a net force
acts to change its speed or direction
- Newton’s 3rd law - for every force, there is always an equal and opposite reaction force
Why do objects move at constant velocity if no force acts on them?
find more resources at oneclass.com
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Document Summary
Speed: rate at which objects move speed=distance/time (units of m/s) Acceleration: rate of change in velocity - units of speed/time (m/s^2) All falling objects at the same rate (not counting friction of air resistance). On earth, g=10 m/s^2: speed increases 10 m/s with each second of falling. Acceleration of gravity: downward velocity increases by about 10 m/s with each passing second. A net force changes momentum, which generally means an acceleration (change in velocity) A force is something that we can feel . Mass - the amount of matter in an object. Weight - the force that acts upon an object. Weightlessness is due to a constant state of freefall. Realized the same physical laws that operate in earth also operate in the heavens. Newton"s first law of motion - an object moves at a constant velocity unless a net force acts to change its speed or direction.
