Forces and Momentum

• Newton's FIRST LAW OF MOTION says that a Resultant Force is required to change the motion of an object

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  If the Resultant force on a Stationary object is 0, the object will remain stationary
• Newton's SECOND LAW OF MOTION says if a Non-Zero Resultant Force acts on an object, it will cause the object to accelerate in that direction
• SECOND Law of Motion:

  The size of the Resultant Force is Directly Proportional to the Acceleration it causes

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  If the Resultant Force is twice as big, the Acceleration it causes will also be twice as big
• Inertia is the tendency for the motion of an object to remain unchanged, like Newton's First Law
• Newton's THIRD LAW OF MOTION states when two objects interact, the forces they exert on each other are equal and opposite

  A) Contact

  
• When two forces are applied to a spring, it can either compress, stretch or bend

  A) Compress

  B) Strech

  C) Bend

  
• If an object returns to its original shape after the force has been removed, this is called Elastic Deformation
• If an object DOESN'T return to its original shape (stays deformed) after the force has been removed, this is called Inelastic Deformation
• Elastic Limit - The maximum stress that an elastic material can withstand without undergoing permanent change in length/shape
• As we increase the amount of force added to the spring, the extension will increase proportionally, therefore:

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  Force ∝ Extension

  
• Spring Constant is how many Newtons it would take to stretch the object by 1 Metre
• In this Graph, Force is directly proportional to the Extension. This is called Hooke's Law

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  When the line starts to curve, this is what we call the Elastic Limit, where the object will no longer return to its original shape. It has been Inelastically Deformed.

  A) Elastic Limit

  
• The term 'Deformation' refers to a change in the shape of an object as a result of forces being applied to it
• The Thinking Distance is how far the car travels before the driver has time to react

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  Thinking Distance depends on:

  • Speed (the faster you go, the further you'll travel)
  • Reaction time (anything that makes the driver distracted will increase the reaction time)
• The Braking Distance is the distance taken for the car to stop using the Brakes

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  The Braking Distance depends on:

  • Speed of the car
  • Mass of the car
  • Friction on the road (ice or rain)
  • If the Brakes are worn/faulty, the car will travel further before it stops

  As both of them increase the Kinetic Energy of the car, which need to be reduced to ZERO
• As the Speed of a car increases, the Total Stopping Distance increases at a much faster rate than proportionally

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  It will increase by factor X (Squared), (x2

  
• The Law Conservation of Momentum states that:

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  In a CLOSED System...

  Total Momentum Before [collision] = Total Momentum After [collision]
• If the Momentum is Positive, then the object will move to the right.

  If the Momentum is Negative, then the object will move to the left
• Cars are equipped with safety equipment to help slow the rate in which the Momentum is lost. This results in a lower force on the vehicle:

  • Air Bags
  • Crumple Zones
  • And Seatbelts
• A Moment is a rotational, or turning effect of a Force

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  If you apply force onto the end of this spanner here, it will rotate around the central point, called a Pivot

  A) Pivot