Force of reaction of a support belongs to elastic forces, and is always directed perpendicular to a surface. It resists to any force which forces a body to move perpendicular to a support. To calculate it it is necessary to reveal and learn numerical value of all forces which affect the body standing on a support.
It is required to you
- - scales;
- - speedometer or radar;
- - angle meter.
1. Determine body weight by scales or any other way. If the body is on a horizontal surface (and it is unimportant, it moves or stays at rest), then force of reaction of a support is equal to the gravity operating on a body. To calculate it increase body weight by the acceleration of gravity which is equal to 9.81 m/s² to N=m•g.
2. When the body moves on the inclined plane directed at an angle to the horizon, force of reaction of a support is at an angle in gravity. At the same time it compensates only that component of gravity which works perpendicular to the inclined plane. For calculation of force of reaction of a support, by means of the angle meter measure a corner under which the plane is located to the horizon. Calculate force of reaction of a support, having multiplied body weight on the acceleration of gravity and a cosine of the angle under which the plane is to N=m horizon • g· Cos(α).
3. In case the body moves on a surface which represents a part of a circle with R radius, for example, the bridge, a hillock that force of reaction of a support considers force operating in the direction from the center of a circle, with the acceleration equal centripetal, acting on a body. To calculate force of reaction of a support in the top point, from acceleration of gravity take away the speed square relation to the radius of curvature of a trajectory.
4. Increase the turned-out number by the mass of a moving body of N=m • (g-v²/R). Speed has to be measured in meters per second, and radius in meters. At a certain speed the value of the acceleration directed from the center of a circle can even out, and even to exceed acceleration of gravity, at this moment the coupling of a body with a surface will be gone therefore, for example, to motorists, it is necessary to control accurately speed on such sections of the road.
5. If the curvature is directed down, and a body trajectory concave, then calculate force of reaction of a support, having added the relation of a square of speed and radius of curvature of a trajectory to acceleration of gravity, and increase the turned-out result by N=m body weight • (g+v²/R).
6. If friction force and coefficient of friction is known, calculate force of reaction of a support, having divided friction force into this coefficient of N=Fтр/μ.