Week 6 pre-work Newton's Laws of Motion

Force

  • An object at rest requires a force to initiate movement, while a moving object needs a force to alter its velocity.

  • Force is a vector quantity, possessing both magnitude and direction.

  • The magnitude of force can be measured using a spring scale.

Newton's First Law of Motion

  • Every object maintains its state of rest or uniform velocity in a straight line unless acted upon by a net force.

Reference Frames

  • Measurements of position, distance, or speed are relative to a reference frame.

  • Newton’s first law is not valid in every reference frame, especially those accelerating or rotating.

  • An inertial reference frame is one in which Newton’s first law holds true, excluding rotating and accelerating frames.

Newton's Second Law of Motion

  • Newton’s second law describes the relationship between acceleration and force.

  • A force is required to change an object's direction or speed.

  • More force results in greater acceleration; the same force exerted on a more massive object yields less acceleration.

  • Mass quantifies an object's inertia and is a measure of the quantity of matter in the object.

  • Mass is not weight; mass is an object's property, while weight is the force exerted on the object by gravity.

  • In the SI system, mass is measured in kilograms (kg).

  • In two and three dimensions, the equation is valid along each coordinate axis.

  • The unit of force in the SI system is the newton (N).

F=MA, where F represents force, M represents mass, and A represents acceleration, illustrating the fundamental relationship between these quantities.

Newton's Third Law of Motion

  • Whenever one object exerts a force on a second object, the second object exerts an equal force in the opposite direction on the first object.

  • A key aspect of the third law is that the forces are exerted on different objects.

  • The first subscript denotes the object upon which the force is exerted; the second indicates the source of the force.

Weight or the Force of Gravity

  • Weight is the force exerted on an object by gravity.

  • Near the Earth's surface, where gravitational force is nearly constant, the weight of an object of mass mm is calculated as: W=mgW = mg

The Normal Force

  • An object at rest must have no net force acting on it.

  • If an object is resting on a table, the force of gravity is present, but an additional force is required to counteract it.

  • The force exerted perpendicular to a surface is termed the normal force.