In physics or mathematics, when they solve various kinds of problems, they use certain approximations. One such approximation is the concept of a material point. Consider in the article the question of whether the car can be considered a material point.
The concept of the point of material
Before answering the question whether the car can be considered the material point, we will get acquainted with the concept itself.
As the name implies, a material point is an immeasurable object that has inertial properties, that is, a finite mass. In life, of course, such an object does not exist, since all bodies have finite geometric dimensions and occupy some volume in space. However, this idealized concept turns out to be convenient in solving a number of motion problems.
Isaac Newton began to work with material points when he formulated his laws of translational motion in classical mechanics.
The dimensions of the body (but not its mass) can be neglected when it is necessary to find the acceleration of the body, if an external force is applied to it, or when it is necessary to calculate the path traveled by it. In other words, many issues of kinematics and dynamics of linear motion are solved using the concept of a material point.
When a car can be regarded as a material point
Can a car be considered a material point if it is necessary to solve the problem of determining its speed, or acceleration, reported by the torque of its engine? Yes, in all these cases, only the mass of the vehicle is important, and not its dimensions.
The main criterion when you can talk about a material point, and when you can not, are traveled distances. So, if a car travels tens of kilometers, then, of course, few people are interested in its geometry.
In what tasks is the car a material point is not
Can a car be considered a material point in physics if one considers its collision. No. Moreover, in this case, not only the dimensions of the car are important, but also the mechanical properties of the material from which it is made. The latter determine the absorption energy upon impact.
If a car is considered as a system of external forces acting on it, then there can be no talk of a material point either. This situation arises, for example, when considering not only the traction force, but also the rolling friction forces of the vehicle wheels or the sliding forces when the car enters into a turn at high speed.
Thus, we can draw the following conclusion: when considering the kinematics of translational motion, as well as dynamics in the case of the action of one external force, when the distance traveled is much larger than the size of the car, it can be considered a point with a final mass; if the task involves the presence of several forces acting on different parts of the car, then its dimensions must be taken into account.