If the resultant force on an object is zero, this means: Operationally, the masses of objects are determined by comparison with the standard kilogram.According to Newton's First Law of motion, an object remains in the same state of motion unless a resultant force acts on it. In practice, it is very difficult to count and identify all of the atoms and molecules in an object, so masses are not often determined in this manner. The mass of an object is the same on Earth, in orbit, or on the surface of the Moon. Unlike weight, mass does not vary with location. The quantity or amount of matter in an object is determined by the numbers of atoms and molecules of various types it contains. Roughly speaking, mass is a measure of the amount of “stuff” (or matter) in something. The inertia of an object is measured by its mass. It is obviously more difficult to change the motion of a large boulder than that of a basketball, for example. As we know from experience, some objects have more inertia than others. Newton’s first law is often called the law of inertia. The property of a body to remain at rest or to remain in motion with constant velocity is called inertia. The genius of Galileo, who first developed the idea for the first law, and Newton, who clarified it, was to ask the fundamental question, “What is the cause?” Thinking in terms of cause and effect is a worldview fundamentally different from the typical ancient Greek approach when questions such as “Why does a tiger have stripes?” would have been answered in Aristotelian fashion, “That is the nature of the beast.” True perhaps, but not a useful insight. Identifying these laws is like recognizing patterns in nature from which further patterns can be discovered. The idea of generally applicable or universal laws is important not only here-it is a basic feature of all laws of physics. Experiments have thoroughly verified that any change in velocity (speed or direction) must be caused by an external force. Newton’s first law is completely general and can be applied to anything from an object sliding on a table to a satellite in orbit to blood pumped from the heart. Additionally, if we know enough about the friction, we can accurately predict how quickly the object will slow down. However, when the air is turned on, it creates a nearly frictionless surface, and the puck glides long distances without slowing down. When the air is turned off, the puck slides only a short distance before friction slows it to a stop. The object would not slow down at all if friction were completely eliminated. Friction is thus the cause of the slowing (consistent with Newton’s first law). Extrapolating to a frictionless surface, we can imagine the object sliding in a straight line indefinitely. If we make the surface even smoother by rubbing lubricating oil on it, the object slides farther yet. If we spray the surface with talcum powder to make the surface smoother, the object slides farther. For example, consider what happens to an object sliding along a rough horizontal surface. The idea of cause and effect is crucial in accurately describing what happens in various situations. If friction disappeared, would the object still slow down? An object sliding across a table or floor slows down due to the net force of friction acting on the object. We will define net external force in the next section. Rather than contradicting our experience, Newton’s first law of motion states that there must be a cause (which is a net external force) for there to be any change in velocity (either a change in magnitude or direction). Note the repeated use of the verb “remains.” We can think of this law as preserving the status quo of motion. A body at rest remains at rest, or, if in motion, remains in motion at a constant velocity unless acted on by a net external force.

What is newtons first law of motion