forces

• Isaac Newton created three laws of motion in 1687 to describe the relationship between a body and the forces acting upon it, and how the body moves in response to those forces
• A force is a push or a pull
• Contact forces arise between two objects which are in contact
• Non-contact forces act between two objects which are not in contact
• Contact forces are forces that act between two objects which are physically touching each other
• Example: Force of friction - Two objects sliding past each other experience friction forces, such as a box sliding down a slope
• Friction is a force that always opposes motion and acts in the opposite direction to the one in which the box is moving
• The resultant force is the single force that has the same effect as two or more forces acting together.
• Two forces that act in the same direction produce a resultant force that is larger than either individual force.
• You can easily calculate the resultant force of two forces that act in a straight line in the same direction by adding their sizes together.
• Two forces that act in opposite directions produce a resultant force that is smaller than either individual force.
• To find the resultant force subtract the magnitude of the smaller force from the magnitude of the larger force.
• Newton’s First Law states that a body will remain at rest or continue to move at constant speed in a straight line, unless a resultant force acts on it.
• Balanced forces have no effect on an object.

  If it is at rest, it remains at rest.

  If it is moving at constant speed in a straight line, it continues to move at the same speed in the same straight line.
• A resultant force is the single forceacting on the object when all the individual forces have been combined.
• When the forces acting on an object do not balance, the resultant force causes the object to accelerate in the direction of the resultant force.
• Acceleration is directly proportional to resultant force if the mass remains constant.
• Acceleration is inversely proportionalto mass if the resultant force remains constant.
• In other words, a resultant force on a body will cause it to change its velocity.

  This simply means that unbalanced forces will cause:

  • acceleration
  • deceleration
  • change in direction
• Resultant force F = mass m x acceleration a
• The Independent Variable is what we change or control in the experiment.

  The Dependent Variable is what we are testing and will be measured in the experiment.

  The Control Variables are what we keep the same during the experiment to make sure it’s a fair test. 
• Stretching force F=spring constant k x extension e

  F = ke
• An object, such as a spring, stores elastic potential energy when stretched or squashed.

  When an object, such as a spring, is stretched, the increased length is called its extension.
• Hooke's law: The extension of a spring is directly proportional to the force applied, provided that the limit of proportionality is not exceeded.
• Pressure is the effect of a force over an area.

  It is the force acting over 1 m2.

  Therefore, the definition of pressure is: pressure is the force per unit area.