Physics

Physics

Forces
1. Frictional Force
  1. A force that Opposes the movement of the sufaces
    1. Static Friction
      1. A force acted on a stationary object, this friction must be overcome in order to have movement
      2. Ff,s = µ*Fn
        Ff,s = Frictional Force
        µ= Coefficient of Friction
        Fn= Normal Force
        The coefficients of friction show how easily one object can slide against another.
    2. Kinetic Friction
      1. The force that acts against an object that is already in motion.
      2. Ff,s = µ*Fn
        Ff,s = Frictional Force
        µ= Coefficient of Friction
        Fn= Normal Force
        The coefficients of friction show how easily one object can slide against another.
2. Gravitational Force
  1. A force that attracts any object with mass.
    1. Gravitational Force is always directed down and constant near Earth (or any other planet).
  2. Fg = (9.8N/kg)*m
    1. Fg = Gravitational Force
      1. (9.8N/kg) = Ratio between mass and weight on Earth
        m= Mass
        Mass
        Amount of stuff, amount of "matter"
        Universal Quantity
        Measured with a Balance
        Units: Grams/Milligrams
        Weight
        Gravitational Force of an Object
        Location Dependent
        Measured with a Scale
        Units: Newtons
    2. This formula can change on another planet depending on the acceleration due to gravity on the planet.
3. Normal Force
  1. The normal force is the support force exerted upon an object that is in contact with another stable object.
    2. Normal force can change, it does not always equal to the gravitational force. This often occurs when the angle of force application is different (because this can affect the force magnitude).
4. Tensional Force
  1. A pulling force that is exerted on each end of string, a cable, a chain, etc.
5. Spring Force
  1. The spring force is the force exerted by a compressed or stretched spring upon any object that is attached to it.
    1. Note: Springs are alwsys analyzed with force on the vertical axis
      1. There is a linear trend between the FORCE A SPRING EXERTS, and the LENGTH THE SPRING STRETCHES.
        The ratio (or slope) between the spring force and the spring's stretch tells us if the spring is stretched 1 m then the force exerted increases by a value of Newtons.
        Force needed to compress or stretch a spring from equilibrium increases linearly.
  2. Fs = K*ΔX + Fo
    1. Fs = Sping Force
      1. ΔX = Change in Position
        K = Spring Constant
        Fo = State of Equilibrium
    2. This is also known as Hooke's Law
Laws of Motion
1. Newton's First Law of Motion
  1. "A body at rest remains at rest and a body in motion continues to move at a constant velocity unless acted upon by an unbalanced force. "
    1. In the absence of resistive forces (friction, air resistance, etc.), if an object has an unbalanced force acted on it then the speed and/or direction changes.
    2. If an object has balanced force acting on it then the speed and direction is maintained (remains unchanged).
      1. Also known as the "Inertia Law"
2. Newton's Second Law of Motion
  1. "A force acting on a body gives it an acceleration which is in the direction of the force and has magnitude inversely proportional to the mass of the body:."
    1. FNet= m*a
      1. FNet = Net Force
        m = mass
        a = acceleration
  2. Relationship between net force and acceleration
    1. If the resultant force increases, then acceleration increases in the condition that the object stays the same.
      1. Force directly affects acceleration because unbalanced forces cause acceleration.
3. Newton's Third Law of Motion
  1. "For every action there is an equal but opposite reaction."
    1. Forces always come in pairs - equal and opposite action-reaction force pairs.
4. Balanced Forces
  1. When a force PRODUCES a change in motion
    1. Constant change in motion
      1. Resultant Force (Net Force) is NOT ZERO
        State of equlibrium
5. Unbalanced Forces
  1. When a force DOES NOT PRODUCE a change in motion.
    1. Constantly accelerating motion
      1. Resultant Force (Net Force) is ZERO
        Unbalanced = Object is Accelerating
Kinematics and Motion
1. Vectors
  1. A quantity that has both magnitude and direction.
    1. Example(s):: Velocity, displacement & acceleration
      1. Displacement
        A vector quantity that describes an object's change in motion relative to it's starting position.
        ΔX = (1/2)*a*Δt^2
        ΔX = Change in Position
        a = acceleration
        Δt = Change in Time
        Displacement can also be determined by finding the area under the curve of the velocity-time graph.
      2. Velocity
        A vector quantity that describes the rate at which an object changes its position.
        V=Δx/Δt
        V = Velocity
        ΔX = Change in Position
        Δt = Change in Time
      3. Acceleration
        A vector quantity that describes the rate at which an object changes its velocity.
        A=Δv/Δt
        A = Acceleration
        ΔV = Change in Velocity
        Δt = Change in Time
        Acceleration can be determined by finding the slope of the velocity time graph which is exactly what the equation: A=Δv/Δt does.
2. Scalers
  1. A quantity that has magnitude but NO direction.
    1. Example(s): time & speed
      1. Distance
        A scalar quantity that describes how much an object has traveled.
      2. Speed
        A scalar quantity that describes how fast an object is moving.
Constant Accelerated Particle Motion
1. Speed Increasing in Positive Direction
  1. 1. The slope of the position-time graph is increasing and positive; this represents the velocity. The slope of the velocity-time graph is constant and positive; this represents acceleration.
2. Speed Increasing In Negative Direction
  1. 1. The slope of the position-time graph is increasing and negative; this represents the velocity. The slope of the velocity-time graph is constant and negative; this represents acceleration.
3. Speed Decreasing in NEgative Direction
  1. 1. The slope of the position-time graph is decreasing and negative; this represents the velocity. The slope of the velocity-time graph is constant and positive; this represents acceleration.
4. Speed decreasing in Positive Direction
  1. 1. The slope of the position-time graph is decreasing and positive; this represents the velocity. The slope of the velocity-time graph is constant and negative; this represents acceleration.

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	Created by Niat Habtemariam about 9 years ago