Physics Assessment Task Research- Moving About

Essay by rarwdinosaursHigh School, 11th gradeA-, July 2007

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Inertia and Newton’s First Law of MotionInertia is the tendency for a body to resist changes in its velocity (that is, acceleration). The Law of Inertia (Galileo is credited for its discovery) also relates to Newton’s First Law of Motion that states that:From both Newton’s first law and Galileo’s law of inertia, we can conclude that forces are not required to keep an object’s velocity going, but instead, forces are required to change an object’s velocity – to accelerate.

However, situations in everyday life seem to contradict this law. A book sitting on a desk with a velocity of 0 ms^-1 can be pushed along a table (the inertia is overcome) but eventually comes to a stop. Aristotle believed that this was due to the fact that there was no more force to keep the book going. However, Newton believed that is was because there were forces acting against the book (in this case, friction) that retarded the forward force of the book.

Another example is one of a driver in a car on a flat road, she still must press down on the accelerator in order for the car to move at a constant speed. It appears she is applying a net force by increasing the driving force. However, all she is doing is balancing out the forces that are acting against the car – friction and air resistance, which explains why she is not accelerating – the forces are in equilibrium. (see figure 1) If the car was simply coasting along on a level road, it would come to a rest even though Newton’s First Law states that it should keep going since there is no obvious net force. We have overlooked the fact that we do not live in a vacuum and that friction and air resistance...