Instruction

1

To determine the speed of uniform motion it is necessary to divide the length of the path travelled in the time it took this path:

v=s/t where:

v is the rate

s – length of the traversed path, and

t - time

Note.

Previously, all units should lead to the same system (preferably SI).

Example 1

Speeding up to maximum speed, the car traveled one kilometer in half a minute, then slowed down and stopped.

Determine the maximum speed of the car.

Solution.

After the acceleration the car was moving at maximum speed, it is the conditions of the problem can be considered uniform. Therefore:

s=1 km,

t=0.5 min.

Driven units of time and distance traveled to a single system of units (SI):

1 km=1000 m

0.5 min= 30 sec

So, the maximum speed of the car:

1000/30=100/3=33 1/3 m/s, or approximately: 33,33 m/s

A: maximum vehicle speed: 33,33 m/s.

v=s/t where:

v is the rate

s – length of the traversed path, and

t - time

Note.

Previously, all units should lead to the same system (preferably SI).

Example 1

Speeding up to maximum speed, the car traveled one kilometer in half a minute, then slowed down and stopped.

Determine the maximum speed of the car.

Solution.

After the acceleration the car was moving at maximum speed, it is the conditions of the problem can be considered uniform. Therefore:

s=1 km,

t=0.5 min.

Driven units of time and distance traveled to a single system of units (SI):

1 km=1000 m

0.5 min= 30 sec

So, the maximum speed of the car:

1000/30=100/3=33 1/3 m/s, or approximately: 33,33 m/s

A: maximum vehicle speed: 33,33 m/s.

2

To determine the velocity of a body in uniformly accelerated motion it is necessary to know the initial speed and rate of acceleration or other related parameters. Acceleration can be negative (in this case, it is, in fact, braking).

Velocity equals initial velocity plus acceleration multiplied by time. In a formula it is written as follows:

v(t)= v(0)+at, where:

v(t) is the velocity of the body at time t

v(0) is the initial velocity of the body

a – acceleration

t is the time elapsed since beginning of acceleration

Note.

1. Is meant motion in a straight line.

2. The initial velocity, as acceleration can be negative relative to the selected direction.

3. The acceleration of gravity usually taken as 9.8 m/S2

Example 2

With the roof down, threw a brick at a speed of 1m/s in 10 seconds, he floated to the ground.

Which was equal to the speed of the brick at the time of landing?

Solution.

Since the direction of the initial velocity and free fall acceleration are the same, the speed of the brick at the surface will be equal to:

1+9,8*10=99 m/s.

Air resistance in problems of this kind, as a rule, not taken into account.

Velocity equals initial velocity plus acceleration multiplied by time. In a formula it is written as follows:

v(t)= v(0)+at, where:

v(t) is the velocity of the body at time t

v(0) is the initial velocity of the body

a – acceleration

t is the time elapsed since beginning of acceleration

Note.

1. Is meant motion in a straight line.

2. The initial velocity, as acceleration can be negative relative to the selected direction.

3. The acceleration of gravity usually taken as 9.8 m/S2

Example 2

With the roof down, threw a brick at a speed of 1m/s in 10 seconds, he floated to the ground.

Which was equal to the speed of the brick at the time of landing?

Solution.

Since the direction of the initial velocity and free fall acceleration are the same, the speed of the brick at the surface will be equal to:

1+9,8*10=99 m/s.

Air resistance in problems of this kind, as a rule, not taken into account.

# Advice 2: How to determine the speed of the car

Vehicle speed is constantly changing during the trip. Determine what speed the car had at one time or another way, very often involved in both the motorists and the competent authorities. Especially because ways to learn the speed of the car a huge amount.

Instruction

1

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.

2

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.

3

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.

4

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.

5

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).