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

Info iconThis preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon
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
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 2
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 5

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

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online