The body which moves has kinetic energy. Its change is result of mechanical work. It is possible to increase kinetic energy, having performed work over a body or having changed its parameters.
It is required to you
- - concept about mechanical work;
- - concept of weight and speed;
- - calculator.
Instruction
1. Generally increase kinetic energy of a body, having performed over it work. For this purpose work on a body by force which will move it on some distance so that the body increased the speed. The work performed over a body will also be equal to increase in its kinetic energy. For example, if it is known that force of draft of the engine of the car is 2000 N, then throughout 100 m the work equal to the work of force on distance A=2000•100=200000 J. Eto will be made and there will be that size by which kinetic energy of the car increased.
2. It is possible to increase kinetic energy also in other ways. As this size depends on weight and the speed of a body (it is equal to a half of the work of body weight of m on v body speed square; Ek=m • v?/2), change these parameters. If to find an opportunity to increase body weight at the same speed which it has then its kinetic energy will increase in as much time when body weight increased. For example, having increased the mass of the moving train twice, receive the same increase in its kinetic energy.
3. It is possible to increase kinetic energy due to increase in speed of a moving body more effectively. It is connected with the fact that kinetic energy is directly proportional to a speed square. Thus, with increase in speed of a body in n of times, kinetic energy will increase in n?. For example, if to increase the speed of a moving body by 3 times, then its kinetic energy will increase by 9 times.
4. Example. How much kinetic energy of the train will increase if in result of loading its weight increased twice, and it moves with a speed, in 1.5 exceeding that which it when it moved empty had. As kinetic energy is calculated on a formula Ek=m • v?/2 where m is body weight, and v is its speed. At increase in weight and speed, according to a condition we will receive: Ek=2 • m • (1.5•v)?/2=2•1.5? • m · v?/2=4.5·m· v?/2. Kinetic energy will increase by 4.5 times.