Instruction

1

In order to calculate the

**force**of sliding friction (Fтр), you need to know the time**of braking**and stopping distance.2

If you know the time

**of braking**, but not known for its braking distance, you can calculate by the formula:s = υ0⋅t/2, where s is the stopping distance, t – time**braking**, υ0 is the velocity of the body at the beginning of**braking**.To calculate the speed of the body at the beginning**of the braking**you'll need to know the braking distance and time**of braking**. Calculate it by the formula:υ0 = 2s/t, where υ0 is the velocity of the body at the beginning of**braking**, s – stopping distance, t – time**braking**.3

Note that the stopping distance is proportional to the square of the initial speed before

**braking**and inversely proportional to the magnitude of the force of sliding friction (power**braking**). That is why, for example, on dry roads (when calculating for cars) shorter braking distance than slippery.4

Once you become aware of all the values, substitute them in the formula: Fтр = 2m⋅s/t2, where FTR silyl sliding friction (power

**braking**), m is the mass of a moving body, s is the braking distance, t – time**braking**.5

Knowing

**the power of****braking**, but not knowing his time, you can make the necessary calculations according to the formula:t = m⋅υ0/ Fтр, where t is the time**of braking**, m is the mass of the moving body, υ0 is the velocity of the body at the beginning of**braking**, FTR silyl**braking**.6

Calculate the

**force**of sliding friction according to another equation:Fтр = μ⋅ Fнорм where FTR silyl sliding friction (power**braking**), μ – coefficient of friction, Fнорм – force of normal pressure of the pressing body to the support (or mg).7

Determine the coefficient of friction experimentally. In school textbooks in physics it is usually already indicated in the conditions of the problem, if you do not want to calculate it for some particular body during laboratory work. To do this, place the body on an inclined plane. Determine the angle at which the body starts moving, and then find out the tables or independently calculate the tangent values of the angle α (the ratio of opposite over adjacent). This will be the value of the coefficient of friction (μ = tg α).