Newton's First Law:
Sir Isaac Newton, in his book Philosophiae Naturalis Principia Mathematica, founded the study of dynamics. Dynamics is the study of motion in terms of mass and force. Mass is the amount of matter present in an object-note that mass differs from weight, which is the force of gravity acting on an object-and force is a push or a pull, or more specifically, something that can cause an acceleration. In his book, Newton proposed three laws governing motion.
Newton's laws of motion altered and expanded upon the ideas of Aristotle and Galileo. Aristotle believed that the natural state of all objects was a state of rest. Therefore, an object in motion would naturally return to rest, and all objects would remain at rest unless induced to move.
Galileo Galilei, an Italian scientist and astronomer, disagreed. He believed a state of motion could be natural just as a state of rest was natural. An object at rest would remain at rest, but, unless induced to change motion, an object in motion would continue to move. Galileo posited that matter tends to resist a change in its state of motion, a property he referred to as "inertia".
Sir Isaac Newton, expanding on Galileo's ideas, stated that an object at rest will remain at rest, and an object in motion will remain in motion, with constant velocity and in a straight line, unless acted upon by an unbalanced force.
Unbalanced force refers to a force not canceled out by another force acting on the object. Force is a vector quantity. In a free body diagram, which shows the forces acting on an object of interest, the object is represented as a point, and the forces acting on it as vectors extending from the point in the directions in which they act. In determining if an unbounded force exists, the sum of the forces, is found. Vectors can only be added if they act in the same dimension, X or Y. Two dimensional vectors are resolved into their components, and the vector sum found.
Newton's first law predicts that, if the forces acting on an object "balance" and cancel each other out, and the sum of the forces in the X and Y directions equals zero , then the object should be either at rest or moving at a constant velocity.
In summation, Newton's first law states that, when the forces acting on an object balance, and the sum of the forces is zero, an object is either at rest or moving with constant velocity. If the sum of the forces does not equal zero, then the object will accelerate in the direction of the net force.
Newton's laws of motion altered and expanded upon the ideas of Aristotle and Galileo. Aristotle believed that the natural state of all objects was a state of rest. Therefore, an object in motion would naturally return to rest, and all objects would remain at rest unless induced to move.
Galileo Galilei, an Italian scientist and astronomer, disagreed. He believed a state of motion could be natural just as a state of rest was natural. An object at rest would remain at rest, but, unless induced to change motion, an object in motion would continue to move. Galileo posited that matter tends to resist a change in its state of motion, a property he referred to as "inertia".
Sir Isaac Newton, expanding on Galileo's ideas, stated that an object at rest will remain at rest, and an object in motion will remain in motion, with constant velocity and in a straight line, unless acted upon by an unbalanced force.
Unbalanced force refers to a force not canceled out by another force acting on the object. Force is a vector quantity. In a free body diagram, which shows the forces acting on an object of interest, the object is represented as a point, and the forces acting on it as vectors extending from the point in the directions in which they act. In determining if an unbounded force exists, the sum of the forces, is found. Vectors can only be added if they act in the same dimension, X or Y. Two dimensional vectors are resolved into their components, and the vector sum found.
Newton's first law predicts that, if the forces acting on an object "balance" and cancel each other out, and the sum of the forces in the X and Y directions equals zero , then the object should be either at rest or moving at a constant velocity.
In summation, Newton's first law states that, when the forces acting on an object balance, and the sum of the forces is zero, an object is either at rest or moving with constant velocity. If the sum of the forces does not equal zero, then the object will accelerate in the direction of the net force.
Cycling and Newton's First Law:
As stated by Newton's first law, the motion of an object, in this case a bicycle, depend on the forces acting on it. Some forces are always present, while some forces depend on the actions of the rider.
All object are constantly subject to the attractive force of gravity, which accelerates an object downward at a constant 9.8 m/s2 unless canceled by an equal force in the opposite direction. For an object resting on the ground or on a surface, gravity is usually counteracted by normal force. Normal force is a contact force, which a surface exerts perpendicularly to itself on any object resting on it.
Below is a free body diagram representing a bicycle for which and equal zero:
All object are constantly subject to the attractive force of gravity, which accelerates an object downward at a constant 9.8 m/s2 unless canceled by an equal force in the opposite direction. For an object resting on the ground or on a surface, gravity is usually counteracted by normal force. Normal force is a contact force, which a surface exerts perpendicularly to itself on any object resting on it.
Below is a free body diagram representing a bicycle for which and equal zero:
Based on Newton's first law, the above could represent two scenarios. When a bicycle is stopped and not moving, the only two forces acting on it are gravity and the normal force. Thus, this free body diagram could represent a bicycle at rest. But, it could also represent a bicycle moving with constant velocity. Given an ideal, friction-less environment, a bicycle moving at constant velocity would maintain this velocity without the application of force. Therefore, in a friction-less environment, a rider could cease pedaling, and their bicycle would coast at constant speed without stopping.