Friction - Brunswick City Schools

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Transcript Friction - Brunswick City Schools

Newton’s Laws
• First Law of Motion
– An object at rest will stay at rest or an object in
motion will continue to move in a straight line with
constant speed unless an outside force acts on it
• Also called the Law of Inertia
• Equilibrium- object can be at rest or moving with
constant velocity; forces are balanced
• Fnet = ma
• Net Force - the addition of all forces on an object
• Tendency of an object to resist change.
• Example: Pushing a stalled car
• Remember there are 2 types of friction!
• To solve for them:
• Ff= µ FN
• µ- (constant) coefficient of friction
Solving Fnet= 0 Problems
• Draw an FBD
• Resolve forces into x and y components
• Write Fnet= 0 for the vertical forces. Do the
same for the horizontal forces.
• Solve using equations.
• You push a 25 kg wooden box across a wooden
floor at a constant speed. How much force do you
need to exert on the box? (µ=0.20)
• A 150-kg box is sitting on an inclined plane of 26.
What is the coefficient of friction?
• A 1,500 kg car parked on a 7° hill. What
is the coefficient of friction?