physics: newton's laws

• Isaac Newton put forth laws that explain why objects move (or don't) as they do, including his first law, also known as law of inertia.
• An object at rest stays at rest and an object in motion stays in motion unless acted upon by an unbalanced force, according to Newton's first law.
• When forces are balanced, objects at rest have an acceleration of 0m/s/s and stay at rest, and objects in motion have an acceleration of 0m/s/s and stay in motion with the same speed and direction.
• Galileo's reasoning was that moving objects would stop only due to friction.
• Any difference in initial and final height of a rolling ball in a pit would be due to friction, according to Galileo.
• If friction was eliminated, the heights would be the same.
• Forces are not needed to keep an object in motion unless an opposing force is present, according to Newton's first law.
• More mass equals more inertia, as evidenced by a 2kg object moving horizontally at 4m/s which takes 0 net force to keep it moving.
• The state of motion is defined by the velocity, and inertia can be rephrased as the tendency of an object to resist changes in its velocity.
• Not changing velocity means no acceleration, and the tendency of an object to resist acceleration is inertia.
• By substituting standard metric units for force, mass, and acceleration into the equation, 1 Newton equals 1kg · m/s/s can be written.
• The recipe for F=ma is a unit of force equals a unit of mass times a unit of acceleration.
• The acceleration of an object as produced by a net force is directly proportional to the magnitude of the net force, in the same direction as the net force, and inversely proportional to the mass of the object.
• mass is inversely proportional to the acceleration if force is held constant, halving mass results in doubling acceleration.
• 1 Newton is defined as the amount of force required to give a 1-kg mass an acceleration of 1 m/s/s.
• Another way to state Newton’s 1st Law is that if the forces acting upon an object are balanced, then the acceleration will be 0m/s/s.
• Objects at an equilibrium will not accelerate, any object with unbalanced forces will accelerate.
• A net force is proportional to the acceleration if mass is held constant, doubling net force equals doubling acceleration.
• Newton’s 2nd Law states that an unbalanced force causes accelerations, which slows down an object.
• Velocity vs Time Graphs show that when a book changes its state of motion from rest to motion, it encounters an unbalanced force causing accelerations which slow down the book.
• An object is acted upon by an unbalanced force only when there is an individual force that is not being balanced by a force of equal magnitude and in the opposite direction.
• Acceleration is produced by the net force, which is the vector sum of all the forces.
• The bigger the force you use, the faster a toy car will start moving.
• Balanced forces are when the two forces acting on an object are of equal magnitude and opposite direction, maintaining the object at equilibrium.
• Unbalanced forces are when the two forces acting on an object are of unequal magnitude or direction, changing the state of motion of the object.
• A book rests on a table, with two forces acting on it: earth's gravitational pull, a downward force, and the push of the table on the book, a normal force that pushes upward on the book.
• The tractor in an action-reaction force pair pushes forward on the ground, but the ground pushes it backwards.
• In an action-reaction force pair, one object pushes on another object, and the second object pushes back.
• A person is walking in an action-reaction force pair, where the person pushes backwards and the earth pushes forward.
• The elephant’s feet in an action-reaction force pair push backward on the ground, and the ground pushes forward on its feet.
• The tractor in an action-reaction force pair wants to go left, but the rope pulls it right.
• The person in an action-reaction force pair wants to push left, but the rope pulls it right.
• The person in an action-reaction force pair wants to push right, but the rope pulls it left.
• The elephant in an action-reaction force pair wants to push back on the rope, but the rope pulls it forward.
• The forces on this book are balanced because the two forces are of equal magnitude and opposite direction, maintaining the book at equilibrium.
• When forces balance each other, the state of motion is maintained and there is no acceleration.
• Unbalanced forces change the state of motion of the object.
• A book slides right on a table.
• A bus drives down the road and a firefly hits its windshield, both of them have equal forces.
• F frict = μ · F norm is the equation for the magnitude of the frictional force on an object.