Category: Kinetic Energy and Work

A contractor wishes to lift a load of bricks from the sidewalk to the top of a building by means of a winch. We can now calculate how much work the force applied by the winch must do on the load to make the lift. The contractor, however, is much more interested in the rate at which…

We next want to examine the work done on a particle-like object by a particular type of variable force—namely, a spring force, the force from a spring. Many forces in nature have the same mathematical form as the spring force. Thus, by examining this one force, you can gain an understanding of many others. The Spring Force…

We next examine the work done on an object by the gravitational force acting on it. Figure 7-6 shows a particle-like tomato of mass m that is thrown upward with initial speed v0 and thus with initial kinetic energy . As the tomato rises, it is slowed by a gravitational force ; that is, the tomato’s kinetic energy decreases because  does work on the…

Finding an Expression for Work Let us find an expression for work by considering a bead that can slide along a frictionless wire that is stretched along a horizontal x axis (Fig. 7-2). A constant force , directed at an angle  to the wire, accelerates the bead along the wire. We can relate the force and the acceleration with…

If you accelerate an object to a greater speed by applying a force to the object, you increase the kinetic energy K (= mv2) of the object. Similarly, if you decelerate the object to a lesser speed by applying a force, you decrease the kinetic energy of the object. We account for these changes in kinetic energy by…

Kinetic energy K is energy associated with the state of motion of an object. The faster the object moves, the greater is its kinetic energy. When the object is stationary, its kinetic energy is zero. For an object of mass m whose speed v is well below the speed of light, For example, a 3.0 kg duck flying past us at 2.0 m/s…

The term energy is so broad that a clear definition is difficult to write. Technically, energy is a scalar quantity associated with the state (or condition) of one or more objects. However, this definition is too vague to be of help to us now. A looser definition might at least get us started. Energy is a number…

One of the fundamental goals of physics is to investigate something that everyone talks about: energy. The topic is obviously important. Indeed, our civilization is based on acquiring and effectively using energy. For example, everyone knows that any type of motion requires energy: Flying across the Pacific Ocean requires it. Lifting material to the top…