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Work and power
Assume that a material point under constant force
Where
If the angle Write the vectors
Where Then the formula (2.42) for the elementary work looks:
To find the work A of the force
Taking into account the relation (2.43), the expression for the work can be written as:
Thus, the work of a variable force on the final movement of the AB is determined line integral along the trajectory. The unit of work in the CI is the joule, which is, according to (2.42) work of 1 H force on the way to 1 m: 1Jl = 1H In some cases, it is important to know not only the work, but also the time during which work is done. The work that is done per unit of time is called power:
Power is equal to the scalar product of vectors of force and velocity. Formula (2.46) can be written in terms of the projections on the coordinate axes:
From (2.46) followed that the power can be increased by increasing both the force and velocity. If the power is given as a function of time, the work can be determined for a period of time from The CI unit of power is Watt: 1 W - is the power at which 1s. the work of 1 Jl is performed.
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