What is force?
The word “force” generally denotes a push or a pull. Now it is not possible to describe a force as we can describe some material object such as an apple. We can only say what force can do. When a body is acted upon by a resultant force it will begin to move. If the body is already moving a force may alter its speed or alter its direction of motion or else bring it to rest. We therefore define force as follows:
Force is that which changes a body’s state of rest or of uniform motion in a straight line.The relation between force and motion will be discussed more fully in a later hater. Another way of expressing this would be to say that a force causes a body to a celebrate (see page 23). We define our unit of force in terms of the acceleration -produced when the force acts on a mass of one kilogram. This unit of force is called the newton (N) and is defined as follows.-A newton is the force required to give a ass
of one kilogram an acceleration of one meter per second”. The newton received its name in hon our of Sir Isaac Newton who laid the foundations of the study of the relation between force and motion in the seventeenth century. We shall see later (page 37) how this definition is related to one of Newton’s laws of motion. It is useful to think of a newton as being roughly equal to the weight of a 100 g mass.