The easiest way to determine the speed of the car is familiar to all from school. To do this you need to fix the quantity of kilometers you drove and the time in which you overcame the distance. The speed of the car is calculated according to the formula: distance (km) divided by time (h). So you will get the desired number.
The second variant is used when the vehicle stopped abruptly, but the basic measurements like time and distance, nobody spent. In this case, the vehicle speed is calculated by its stopping distance. For such a calculation even has its own formula. But it can be used only if the left braking marks on the road.
So, the formula is as follows: the initial velocity of the car is equal to 0.5 x the rise time deceleration (m/s) x, the steady-state deceleration of the car when braking (m/S2) + root of the length of the braking path (m) x, the steady-state rate of vehicle deceleration during braking (m/S2). The value called "steady-state deceleration of the car when braking" is fixed and only depends on what the asphalt was the place to be. In case of dry road in the formula, substitute the number of the 6.8 it is written in a FR used for calculations. For wet asphalt this value will be equal to 5.
To determine the speed on braking distance, and another according to the same formula. It looks like this: S = Ke x V x V / (254 x FS). To substitute in this formula have the following values: braking coefficient (Ke) for passenger cars during this value is usually taken 1, speed at beginning of braking (V), coefficient of traction (FS) for different weather conditions identified its value: dry pavement - 0,7, wet road - 0,4, Packed snow - 0,2, icy track is 0.1.
You can determine the speed of the car in a certain gear. For this you need following values: the number of revolutions of the crankshaft (Nc), dynamic wheel radius (R), the gear ratio (in), gear ratio of a pair (irn), the initial vehicle speed (Va). Calculate the speed according to the formula: Va = Nc x 60 x 2pi x R / (1000 x in x irn).