Another common expression of power is the horsepower, where 1 horsepower is equal to 746 watts.įorces cause acceleration (a change in velocity). This is the standard unit of measurement, but power can be expressed by any means of energy over time. One watt is equal to one joule per second, where joule is the unit of energy. One newton is the force required to accelerate a one kilogram mass at a rate of one meter per second squared, or kg In scientific applications, force is measured in newtons, and in the English system it’s expressed in pounds. If a person runs and then walks up the same flight of stairs, the same amount of work is done both times, but more power is generated while running, because the same amount of work is being performed in less time. 146) by acceleration ( Earth’s gravity is 9.8 meters per second), which equals 1.43 newtons. To calculate the force in newtons of a baseball that weights 146 g, you simply multiply the mass (in kilograms, so. When a baseball player hits a ball, the bat exerts force on the ball (and vice versa). Where P is power, W is work and t is time.įorce is inherent in the interaction of any and all objects. Where F is the force, m is mass and a is the gravitational acceleration.Īs a rate of change of work done or the energy of a subsystem, power is calculated as: So, force is one element of the power equation, along with other basic elements like distance and time.įorce is calculated as a product of mass and gravitational acceleration, and is usually denoted as Power expresses how quickly that work is done. But if a person pushes on a table and moves it, then there is work. For example, a person pressing against a brick wall is consuming energy, but no work is being done and no power created because the wall does not move. Work occurs when there is force causing movement of an object. Another way to put this is: the rate at which “work” is done. Power is defined as the amount of energy consumed per unit of time. Force is a fundamental expression of physical occurrences, as are time and distance. At-a-distance interaction occurs through forces like gravity and magnetism. Examples of direct contact forces include the friction of car tires on a road, or the air resistance on a moving car. Whenever objects interact, they push or pull one another, whether through direct contact or at-a-distance contact. A force can only occur when objects are interacting.
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