Guide

1

To determine the speed of uniform motion to divide the length of the distance traveled in the time it took this path:

v = s / t, where:

v - is the speed,

s- the length of the distance traveled, and

t - time

Note.

Previously, all units should be brought to a system (preferably SI).

Example 1

accelerate to maximum speed, the car drove one kilometer in half a minute, then pulled up and stopped.

Determine the maximum speed of the vehicle.

decision.

Since after the dissolution of the car was moving at top speed, it under the terms of the problem can be considered uniform.Therefore:

s = 1 km,

t = 0,5 min.

Here are the units of time and distance traveled in one system (SI):

1 km = 1000 m

0,5 min = 30 sec

means that the maximum speed of the vehicle:

1000/30 = 100/3 = 33 1/3m / s, or
approximately: 33.33 m / s

A: top speed: 33.33 km / s.

v = s / t, where:

v - is the speed,

s- the length of the distance traveled, and

t - time

Note.

Previously, all units should be brought to a system (preferably SI).

Example 1

accelerate to maximum speed, the car drove one kilometer in half a minute, then pulled up and stopped.

Determine the maximum speed of the vehicle.

decision.

Since after the dissolution of the car was moving at top speed, it under the terms of the problem can be considered uniform.Therefore:

s = 1 km,

t = 0,5 min.

Here are the units of time and distance traveled in one system (SI):

1 km = 1000 m

0,5 min = 30 sec

means that the maximum speed of the vehicle:

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

A: top speed: 33.33 km / s.

2

to determine the velocity of the body at a uniformly accelerated motion is necessary to know the initial velocity and the acceleration, or other related options.The acceleration may be negative (in this case, in fact, braking).

speed equal to the initial velocity plus acceleration times the time.In a formula is written as follows:

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

v (t) - the speed of the body at time t

v (0) - The initial velocity of the body

and - the value ofacceleration

t - the time elapsed since the start of the acceleration

Note.

1. implies movement in a straight line.

2. The initial rate, as well as the acceleration may be negative relative to the selected direction.

3. The acceleration of free fall is usually taken as equal to 9,8 m / s²

Example 2 with the roof down threw a brick at a speed of 1m / s.After 10 seconds he reached the ground.

What was equal to the rate of bricks on landing?

decision.

Since the direction of the initial velocity and acceleration of free fall of the same, the velocity at the surface of bricks is equal to:

9.8 * 1 + 10 = 99 m / s.

air resistance problems of this kind are usually not taken into account.

speed equal to the initial velocity plus acceleration times the time.In a formula is written as follows:

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

v (t) - the speed of the body at time t

v (0) - The initial velocity of the body

and - the value ofacceleration

t - the time elapsed since the start of the acceleration

Note.

1. implies movement in a straight line.

2. The initial rate, as well as the acceleration may be negative relative to the selected direction.

3. The acceleration of free fall is usually taken as equal to 9,8 m / s²

Example 2 with the roof down threw a brick at a speed of 1m / s.After 10 seconds he reached the ground.

What was equal to the rate of bricks on landing?

decision.

Since the direction of the initial velocity and acceleration of free fall of the same, the velocity at the surface of bricks is equal to:

9.8 * 1 + 10 = 99 m / s.

air resistance problems of this kind are usually not taken into account.