Physics Force. What is force? –Any push or pull that tends to cause a change in motion –measured in Newtons (N) or pounds (lbs) 1 N = 0.225 lbs –examples.

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Physics Force

What is force? –Any push or pull that tends to cause a change in motion –measured in Newtons (N) or pounds (lbs) 1 N = 0.225 lbs –examples of force gravity (weight) magnetism electricity tension or compression

Newton’s Laws of Motion 1st Law - Law of Inertia –An objects motion will remain in motion until acted upon by an outside force. 2nd Law - F = ma –The net force on an object will cause it to accelerate inversely proportional to its mass 3rd Law - Action - Reaction –For every action there is an equal but opposite reaction

Equilibrium Forces are balanced (1st law) The net force (resultant force) is 0 There is no change in motion –a = 0 –v is constant

Friction Friction (THEORY GIVEN BY GALILEO)is dependant on 2 factors, the roughness of the surfaces (coefficient of friction) in contact and the force pushing the surfaces together (normal force) F fric =  F norm Friction may be static (starting or kinetic (moving) You may use subscripts to indicate this. ie.  s or  k

CONTACT FORCES FRICTIONAL TENSIONAL NORMAL AIR RESISTANCE APPLIED SPRING

AT A DISTANCE FORCE GRAVITATIONAL ELETRICAL MAGNETIC

Applied(Fapp) (Force on hanger) Normal force ( Fnorm ) Friction force (F fric ) Gravity (Fgrav) (Force on plane) Forcex-componenty-component AppliedFapp0 Gravity0-W Friction-F fric 0 Normal0 N

Pull(P) (Force on hanger) Normal force ( N ) Friction force (F f ) Weight (W) (Force on plane) Free body diagrams are diagrams that Show all the forces acting on an object Horizontal(equations)

Applied (Force on hanger) Normal force Friction force Gravity (Force on plane) W y =Wcos  W x =Wsin  Forcex-componenty-component AppliedP0 Gravity -Wsin  -Wcos  Friction-F f 0 Normal0 N  F = 0P - F f - Wsin  = 0 N - Wcos  = 0 Incline(components)

Applied (Force on hanger) Normal force Friction force Weight (Force on plane) W y =Wcos  W x =Wsin  As long as the object is sitting still or at constant acceleration  F y = 0  F x = 0 Fapp - F fric - Wsin  = 0 Fnorm - Wcos  = 0 Fapp = F fric + Wsin  Fnorm = Wcos  F f =  N Incline(equations)

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