How is force described

Mass is a physical property of matter that depends on size and shape of matter, and is expressed as kilograms by the SI system. All elements have physical properties whose values can help describe an elements physical state. Changes to these properties can describe elemental transformations. Physical properties do not change the chemical nature of matter. The physical property we are covering in this atom is called mass. The terms mass and weight are often interchanged, however it is incorrect to do so.

Weight is a different property of matter that, while related to mass, is not mass, but rather the amount of gravitational force acting on a given body of matter. Mass is an intrinsic property that never changes. In order to measure something, a standard value must be established to use in relation to the object of measurement. This relation is called a unit. There are other units of mass, including the following only the first two are accepted by the SI system :.

Privacy Policy. Skip to main content. The Laws of Motion. Search for:. Force and Mass. Force Force is any influence that causes an object to change, either concerning its movement, direction, or geometrical construction. Some students think such a force keeps objects moving; and that objects slow down and stop because this force is gradually used up. At this level, it is completely appropriate to describe a force as a push or a pull.

A force is exerted on one object by another. The idea of a force is not limited to living things or non-living things. All objects living and non-living can apply a force on or to another object; also all objects living and non living can be affected by forces. These ideas are also developed in the focus idea Pushes and pulls. A central focus of your teaching at this level should be to emphasise the idea that a push or a pull is called a force.

By observing lots of examples, students will be encouraged to see that both living and non-living things can exert forces on other objects and will be able to recognise when and where forces influence their everyday experiences. Such vector diagrams were introduced in an earlier unit and are used throughout the study of physics.

The size of the arrow is reflective of the magnitude of the force and the direction of the arrow reveals the direction that the force is acting. Such diagrams are known as free-body diagrams and are discussed later in this lesson.

Furthermore, because forces are vectors, the effect of an individual force upon an object is often canceled by the effect of another force. For example, the effect of a Newton upward force acting upon a book is canceled by the effect of a Newton downward force acting upon the book.

In such instances, it is said that the two individual forces balance each other ; there would be no unbalanced force acting upon the book. Other situations could be imagined in which two of the individual vector forces cancel each other "balance" , yet a third individual force exists that is not balanced by another force. For example, imagine a book sliding across the rough surface of a table from left to right.

The downward force of gravity and the upward force of the table supporting the book act in opposite directions and thus balance each other. However, the force of friction acts leftwards, and there is no rightward force to balance it.

In this case, an unbalanced force acts upon the book to change its state of motion. The exact details of drawing free-body diagrams are discussed later. For now, the emphasis is upon the fact that a force is a vector quantity that has a direction. The importance of this fact will become clear as we analyze the individual forces acting upon an object later in this lesson.