Tip 1: How to determine the braking force
Tip 1: How to determine the braking force
The safety of traffic is greatly influenced by the braking power of the car. The better the brakes, the easier it is to lose speed before a sudden obstacle.
You will need
- Straight section of dry and level road
- Construction Roulette
Instructions
1
Find a straight section of the road with a weak movement. Asphalt should be smooth, without pits and trays. Slope in any direction is undesirable. Examine the roadway. Remove rubbish and other objects, the presence of which can affect the safety of traffic. Establish a well-marked milestone. It marks the place where you need to start braking.
2
Use the GPS navigator to measure speed. Automobile speedometers often underestimate the real speed by 5 kilometers or more. The accuracy of the readings is lower the higher the speed of the machine. Braking distance measurements are usually carried out at a speed of 100 kilometers per hour. Install the machine on the roadway in such a way that it is guaranteed to gain the necessary speed to the milestone. Try to find an assistant who will monitor the speed of the car.
3
Make sure that the trafficmeans do not interfere. Start overclocking. The assistant at this time should monitor the speed on the screen of the navigator. As soon as the car accelerates to the required speed, it will signal. Further move without acceleration. As soon as the car is level with the milestone, begin braking until the car stops completely. Try not to block the wheels. In case of skidding, immediately release the brake.
4
Measure the distance from the milestone to the stopping pointcar. It is desirable to repeat the experiment at least three times. Add all the results, divide them by the number of attempts. The average value of the stopping distance will be written in h. Then the work spent on braking: A = F * h, hence F = A / h. Now let's express the work through the speed and mass of the car: A = mV² / 2, where m is the mass of the car, kg; V - initial speed equal to 100 km / h. Substitute the work in the first formula, we obtain an expression for determining the braking force through the stopping distance, the initial speed and the mass of the car: F = mV² / 2h
5
Substitute the results of the experiment into the formula, perform arithmetic operations.
Tip 2: How to find the braking force
Force inhibition Is the sliding friction force. If the force applied to the body exceeds the maximum value Force friction, the body begins to move. The sliding frictional force always acts in the direction opposite to the speed.
Instructions
1
In order to calculate Force friction sliding (Fri), you need to know the time inhibition and the length of the stopping distance.
2
If you know the time inhibition, but its stopping distance is not known, then you can calculate by the formula: s = υ0⋅t / 2, where s is the length of the stopping distance, t is the time inhibition, υ0 is the velocity of the body at the moment of the start inhibition. To calculate the velocity of the body at the time of the start inhibition You will need to know the stop distance and time inhibition. Calculate it according to the formula: υ0 = 2s / t, where υ0 - the speed of the body at the moment of the start inhibition, s - length of the stopping distance, t - time inhibition.
3
Note that the length of the braking distance is proportional to the square of the initial speed before starting inhibition and inversely proportional to the magnitude of the frictional force of sliding (force inhibition). That is why, for example, on a dry road (when calculating for cars), the braking distance is shorter than slippery.
4
After you know all the values, substitute them in the formula: Fmp = 2m⋅s / t2, where Ftr is the sliding friction force inhibition), m is the mass of the moving body, s is the stopping distance, t is the time inhibition.
5
Knowing Force inhibition, but not knowing its time, you can make the necessary calculations by the formula: t = m⋅υ0 / FР, where t - time inhibition, m - mass of the moving body, υ0 - velocity of the body at the moment of the start inhibition, Ftr - force inhibition.
6
Calculate Force sliding friction by another formula: Ftr = μ⋅ FNorm, where Ftr - sliding friction force (force inhibition), μ is the coefficient of friction, Fnorm is the force of the normal pressure that presses the body against the support (or mg).
7
Determine the coefficient of friction experimentally. In school textbooks on physics, it is usually indicated in the conditions of the problem, if it is not necessary to calculate it for a particular body during laboratory work. To do this, place the body on an inclined plane. Determine the angle at which the body starts moving, then learn from the tables or calculate by yourself the tangent of the obtained angle α (the ratio of the opposite leg to the adjacent one). This is the value of the coefficient of friction (μ = tan α).
