At any movement between the surfaces of bodies or in the medium in which it moves, there are always forces of resistance. They are also called frictional forces.
They can depend on the types of rubbing surfaces, the reactions of the support of the body and its speed, if the body moves in a viscous medium, for example, water or air.
You will need
- - dynamometer-
- - table of coefficients of friction-
- - calculator-
- - scales.
Find the strength of resistance to movement, whichActs on a uniformly rectilinearly moving body. To do this, use a dynamometer or other means to measure the force that must be applied to the body so that it moves uniformly and rectilinearly. According to Newton's third law, it will be numerically equal to the strength of the resistance of movement of the body.
Determine the resistance to movement of the body,Which moves along a horizontal surface. In this case, the frictional force is directly proportional to the strength of the support reaction, which in turn is equal to the force of gravity acting on the body. Therefore, the drag force in this case or the friction force Fmp is equal to the product of the mass of the body m, which is measured by weights in kilograms, by the acceleration due to gravity g? 9.8 m / s? And the coefficient of proportionality?, Ftr = ?? m? G. Number? It is called the coefficient of friction and depends on the surfaces that come into contact during motion. For example, for the friction of steel in wood, this coefficient is 0.5.
Calculate the strength of resistance to movement of the body,Moving along an inclined plane. In addition to the coefficient of friction ?, mass of the body m and acceleration of gravity g, it depends on the angle of inclination of the plane to the horizon?. To find the resistance to motion in this case, it is necessary to find products of the coefficient of friction, the mass of the body, the acceleration of gravity and the cosine of the angle at which the plane is inclined to the horizon Fmp =? M? G? Cos (?).
When the body moves in the air on lowThe force of resistance to movement Fc is directly proportional to the speed of movement of the body v, Fc = ?? v. Coefficient ? Depends on the properties of the body and the viscosity of the medium and is calculated separately. When driving at high speeds, for example, when a body falls from a significant height or the vehicle moves, the drag force is directly proportional to the square of the speed Fc = ?? v ?. Coefficient ? Further calculated for high speeds.