The coefficient of rigidity shows what force needs to be applied to a body that it is elastic to deform it per unit length. It is about elastic deformation when the body after impact on it takes the former form again. To find this size, it is necessary to deform a body, having applied to it force, or to measure potential energy of its deformation.
It is required to you
- - calculator;
- - dynamometer;
- - ruler.
Instruction
1. Attach a dynamometer to a body and pull for it, having deformed a body. Force which will be shown by a dynamometer on the module will be equal to the elastic force operating on a body. Find rigidity coefficient, using Hooke's law which says that elastic force is directly proportional to its lengthening and is directed aside, opposite to deformation. Calculate rigidity coefficient, having divided value of force of F into lengthening of a body x which measure by a ruler or a roulette of k=F/x. To find lengthening of the deformed body subtract length of the deformed body from its initial length. The coefficient of rigidity is measured in N/m.
2. If there is no dynamometer, suspend cargo of the known weight to a deformable body. You watch that the body was deformed it is elastic and did not collapse. In this case the weight of cargo will be equal to the elastic force operating on a body which coefficient of rigidity needs to be found, for example, springs. Calculate rigidity coefficient, having divided the work of mass of m and acceleration of gravity of g≈9.81 of m/s² into lengthening of a body x, k=m • g/x. Measure lengthening by the technique offered in the previous point.
3. Example. Under cargo of 3 kg the spring 20 cm long became 26 cm, define its rigidity. At first find lengthening of a spring in meters. For this purpose from length of the extended spring, subtract its length in the normal state x =26-20=6 cm =0.06 m. Calculate rigidity, using the corresponding formula k=m • g/x=3•9,81/0,06≈500 of N/m.
4. When the potential energy is known it is elastic the deformed body, calculate its rigidity. For this purpose in addition measure its lengthening. The rigidity will be equal to the doubled potential energy of ER divided into a square of lengthening of a body x, k=2 • Ep/x². For example, if the ball was deformed on 2 cm and received potential energy of 4 J, then its rigidity k=2•4/0.02²=20000 N/m.