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Flashcards in Physics Class 1 Deck (12)
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Newton's First Law

Law of inertia
- an object in motion tends to stay in motion
- an object at rest tends to stay at rest
- velocity only changes with an applied net force


Newton's Second Law

Fnet = m a
Force ∝ a


What does it mean if Fnet = 0

Velocity is not 0 too, it just means velocity is constant


Weight formula

W = m g


Newton's Third Law

For every action there's an equal & opposite reaction
- do not cancel out
- equal in magnitude and opposite in direction


Normal force

force a surface exerts to keep itself intact
- direction is normal (perpendicular) to surface


Kinetic friction vs static friction

Kinetic friction
Fk = μk Fn
Use: skidding or slipping
- Direction opposes velocity

Static friction
Fs μs Fn
Use: no motion relative to contact surface or rolling without slipping
- Direction opposes other forces


How to know to use μk or μs

1. Find Fsmax ---> μs x Fn
2. Does Fapplied > Fsmax? If yes, use μk because there will be slippage, if not then Fs = Fapp

If yes...
3. Use kinetic friction formula to find the force of friction (Fk = μk x Fn)
* Fn will be in the x direction


Force of tension

Always directed along the rope, away from object it's connected to
- tension is same throughout any single rope


How to calculate acceleration of masses?

1. Set a positive direction of rotation for pulley
2. Determine net force acting on system of masses (tensions cancel out)
3, aooky Fnet = mtotal x a


An object undoing nonzero acceleration is...

- turning at constant speed
- slowing down
- speeding up


Which is larger usually - μs or μk?