- - dynamometer;
- - table of coefficients of friction;
- - Calculator;
- - scales.
find resistance force which acts on the body moving uniformly in a straight line.To this end, using a dynamometer or otherwise measure the force that must be applied to the body that it moves uniformly in a straight line.According to Newton's third law it is numerically equal to the force of resistance to movement of the body.
determine the strength of the resistance movement of the body, which moves on a horizontal surface.In this case, the frictional force is directly proportional to the reaction force support which is in turn equal to the force of gravity acting
on the body.Therefore, resistance force, or in this case, the frictional force is the product of Ftr body mass m, which is measured weights in kilograms by the gravitational acceleration g≈9,8 m / s² and the proportionality coefficient μ, Ftr = μ ∙ m ∙ g.The number μ is called the coefficient of friction depends on the surface coming into contact with the movement.For example, to steel friction coefficient of the wood is 0.5.
Calculate the resistance force of a body moving on an inclined plane.Additionally the coefficient of friction μ, body mass m and the gravitational acceleration g, it depends on the angle of inclination α to the horizontal plane.To find a resistance force in this case, you need to find a product of the friction coefficient, weight, gravitational acceleration and the cosine of the angle at which the plane is inclined to the horizon Ftr = μ ∙ m ∙ g ∙ cos (α).
When a body moves in the air at low speeds resistance force Fc is directly proportional to the velocity of the body v, Fc = α ∙ v.The coefficient α depends on the properties of the body and the viscosity of the medium and is calculated separately.When driving at high speeds, for example, a fall from a considerable height of the body or the vehicle is moving, the resistance force is directly proportional to the square of the speed Fc = β ∙ v².The coefficient β is calculated in addition to high speeds.