# Work - Work constant force Suppose a constant force F acts...

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Suppose a constant force F acts on a body while the object moves over a distance d. Both the force F and the displacement d are vectors who are not necessarily pointing in the same direction (see Figure 7.1). The work done by the force F on the object as it undergoes a displacement d is defined as The work done by the force F is zero if: * d = 0: displacement equal to zero * [phi] = 90deg.: force perpendicular to displacement Figure 7.2. Positive or Negative Work. The work done by the force F can be positive or negative, depending on [phi]. For example, suppose we have an object moving with constant velocity. At time t = 0 s, a force F is applied. If F is the only force acting on the body, the object will either increase or decrease its speed depending on whether or not the velocity v and the force F are pointing in the same direction (see Figure 7.2). If ( F * v ) > 0, the speed of the object will increase and the work done by the force on the object is positive. If ( F * v ) < 0, the speed of the object will decrease and the work done by the force on the object is negative. If ( F * v ) = 0 we are dealing with centripetal motion and the speed of the object remains constant. Note that for the friction force ( F * v ) < 0 (always) and the speed of the object is always reduced ! Per definition, work is a scalar. The unit of work is the Joule (J). From the definition of the work

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Work - Work constant force Suppose a constant force F acts...

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