In physics there is this misconception that \'a force is needed for motion\'. I
ID: 1327414 • Letter: I
Question
In physics there is this misconception that 'a force is needed for motion'.
I have been tasked to write a report on the aboved mentioned line:
1. A problematic area in the teaching and learning of mechanics
2. A critical analysis of various factors relevant to the problematic area identified
3. A critical reflection on how to enhance teaching and learning of the identified problematic area
4. design, the justification a teaching kit to tackle the problematic area
5. Implement, evaluate and reflect on the effectiveness of the teaching kit
I have chosen misconception on "a force is needed for motion" as the problematic area.
I have to write a report based on these five questions
Explanation / Answer
Newtons three laws states that,
Newton's first law states that every object remains at rest or in uniform motion in a straight line unless compelled to change its state by the action of an external force. This is normally taken as the definition of inertia. The key point here is that if there is no net force acting on an object (if all the external forces cancel each other out) then the object maintains a constant velocity. Prior to Newton's investigation, people believed that one needed to constantly apply a force to maintain a constant velocity. Newton's law states quite the opposite; no force is needed to maintain a constant velocity. Forces produce a change in velocity not the velocity itself. If all external forces are balanced and the velocity is zero, then the object remains at rest. If an external force is applied, the velocity changes because of the force.
The second law explains how the velocity changes. The law defines a force to be equal to change in momentum (mass times velocity) per change in time. For an object with a constant mass, the second law can be more easily expressed as the product of an object's mass and it's acceleration.
F = m * a
Acceleration is the change in velocity with change in time. For a constant external applied force, the acceleration is inversely proportional to the mass. For the same force, a lighter object has a higher acceleration than a heavy object. A force causes a change in velocity; and likewise, a change in velocity generates a force. The equation works both ways. Newton developed the calculus of mathematics. The "changes" expressed in the second law are accurately defined in differential forms. Calculus can also be used to determine the velocity and location variations experienced by an object subjected to an external force.
The third law states that for every action (force) in nature there is an equal and opposite reaction. In other words, if object A exerts a force on object B, then object B also exerts an equal force on object A. Notice that the forces are exerted on different objects. The third law can be used to explain the generation of lift by a wing and the production of thrust by a propeller.
uppose there were some rule or formula that said that if an object is going at some speed v, there must have been some force F at some point in the past to start it in motion. Suppose observer A says that a certain object is moving at some speed v, and we calculate the past force F from it. But observer B, using a different frame of reference, could say that the object's velocity was zero. The formula can't hold true for B if it also holds true for A, since they agree on F but disagree on v.
The fundamental idea of Newtonian mechanics is that if we ask why an object is moving, the default explanation is that it was already moving before that.
Newton's first law of motion declares that a force is not needed to keep an object in motion. Slide a book across a table and watch it slide to a rest position. The book in motion on the table top does not come to a rest position because of the absence of a force; rather it is the presence of a force - that force being the force of friction - that brings the book to a rest position. In the absence of a force of friction, the book would continue in motion with the same speed and direction - forever (or at least to the end of the table top)! A force is not required to keep a moving book in motion; and a force is not required to keep a moving sled in motion; and a force is not required to keep any object horizontally moving object in motion.