Physics test on the topic "rectilinear uniform and uniformly accelerated motion." Rectilinear uniform motion Тс 1 displacement speed uniform rectilinear motion

Uniform movement- this is movement at a constant speed, that is, when the speed does not change (v \u003d const) and there is no acceleration or deceleration (a \u003d 0).

Rectilinear motion- this is movement in a straight line, that is, the trajectory of rectilinear movement is a straight line.

Uniform rectilinear motion is a movement in which the body makes the same movements for any equal intervals of time. For example, if we divide some time interval into segments of one second, then with uniform motion the body will move the same distance for each of these segments of time.

The speed of uniform rectilinear motion does not depend on time and at each point of the trajectory is directed in the same way as the movement of the body. That is, the displacement vector coincides in direction with the velocity vector. In this case, the average speed for any period of time is equal to the instantaneous speed:

V cp = v

Distance traveled in rectilinear motion is equal to the displacement modulus. If the positive direction of the OX axis coincides with the direction of movement, then the projection of the velocity on the OX axis is equal to the velocity and is positive:

V x = v, i.e. v > 0

The projection of displacement onto the OX axis is equal to:

S \u003d vt \u003d x - x 0

where x 0 is the initial coordinate of the body, x is the final coordinate of the body (or the coordinate of the body at any time)

Motion equation, that is, the dependence of the body coordinate on time x = x(t), takes the form:

X \u003d x 0 + vt

If the positive direction of the OX axis is opposite to the direction of motion of the body, then the projection of the body velocity on the OX axis is negative, the velocity is less than zero (v< 0), и тогда уравнение движения принимает вид:

X \u003d x 0 - vt

Dependence of speed, coordinates and path on time

The dependence of the projection of the body velocity on time is shown in fig. 1.11. Since the speed is constant (v = const), the speed graph is a straight line parallel to the time axis Ot.

Rice. 1.11. The dependence of the projection of the velocity of the body on time for uniform rectilinear motion.

The displacement projection onto the coordinate axis is numerically equal to the area of ​​the OABS rectangle (Fig. 1.12), since the magnitude of the displacement vector is equal to the product of the velocity vector and the time during which the movement was made.

Rice. 1.12. The dependence of the projection of the movement of the body on time for uniform rectilinear motion.

The plot of displacement versus time is shown in Fig. 1.13. It can be seen from the graph that the velocity projection is equal to

V = s 1 / t 1 = tg α

where α is the angle of inclination of the graph to the time axis. The larger the angle α, the faster the body moves, that is, the greater its speed (the longer the body travels in less time). The tangent of the slope of the tangent to the graph of the dependence of the coordinate on time is equal to the speed:

Tgα = v

Rice. 1.13. The dependence of the projection of the movement of the body on time for uniform rectilinear motion.

The dependence of the coordinate on time is shown in fig. 1.14. It can be seen from the figure that

Tgα 1 >tgα 2

therefore, the speed of body 1 is higher than the speed of body 2 (v 1 > v 2).

Tg α 3 = v 3< 0

If the body is at rest, then the graph of the coordinate is a straight line parallel to the time axis, that is

X \u003d x 0

Rice. 1.14. Dependence of the body coordinate on time for uniform rectilinear motion.

This manual includes training tasks. tests for self-control, independent work, test papers and examples of solving typical problems. Suggested didactic materials compiled in full accordance with the structure and methodology of the textbook A. V. Peryshkin, K. M. Gutnik “Physics. Grade 9".

TK-1. Path and movement.
1. Indicate in which of the following examples the body can be considered a material point:
a) the earth moving around the sun;
b) the Earth rotating around its axis;
c) the moon revolving around the earth;
d) the Moon, on the surface of which the lunar rover moves;
e) a hammer thrown by an athlete;
f) sports hammer, which is made on the machine.
2. What determines the bus passenger by the numbers on the kilometer posts installed along the highway - the movement or the distance traveled by the bus?
3. Figure 1 shows the flight paths of projectiles. Are the paths traveled by the shells equal for these movements? moving?
4. A body thrown vertically upward from point L fell into the shaft (Fig. 2). What are the distance traveled by the body and the displacement module if AB = 15 m, BC - 18 m?
5. The athlete has to run one lap (400 m). What is the displacement modulus if he: a) ran 200 m of the path; b) finished? Consider the stadium track as a circle.
6. The squirrel runs inside the wheel, being at the same height relative to the floor. Are the path and displacement equal in such a motion?

Preface.
TRAINING TASKS
TK-1. Path and movement.
TZ-2. rectilinear uniform motion.
TZ-3. Relativity of motion.
TZ-4. Rectilinear uniformly accelerated motion.
TK-5. Newton's laws.
TZ-6. Free fall of bodies.
TZ-7. Law gravity. body movement
ТЗ-8. Body impulse. Law of conservation of momentum.
Law of energy conservation.
TK-9. Mechanical oscillations and waves. Sound.
TZ-10. Electromagnetic field.
TZ-11. The structure of the atom and the atomic nucleus.
SELF-CHECK TESTS
TS-1. Rectilinear uniform motion.
TS-2. Rectilinear uniformly accelerated motion.
TS-3. Newton's laws.
TS-4. Free fall of bodies.
TS-5. The law of universal gravitation. body movement
around the circumference. artificial satellites Earth..
TS-6. body momentum. Law of conservation of momentum.
Law of energy conservation.
TS-7. Mechanical vibrations.
TS-8. mechanical waves. Sound.
TS-9. Electromagnetic field.
TS-10. The structure of the atom and the atomic nucleus.
INDEPENDENT WORKS
SR-1. Path and movement.
SR-2. Rectilinear uniform motion.
SR-3. Rectilinear uniform motion.
Graphic tasks.
SR-4. Relativity of motion.
SR-5. Rectilinear uniformly accelerated motion.
SR-6. Rectilinear uniformly accelerated motion.
Graphic tasks.
SR-7. Newton's laws.
SR-8. Free fall of bodies.
SR-9. The law of universal gravitation.
Artificial satellites of the Earth.
SR-10. The movement of the body in a circle.
SR-11. body momentum. Law of conservation of momentum.
Law of energy conservation.
SR-12. Mechanical vibrations.
SR-13. mechanical waves. Sound.
SR-14. Electromagnetic field.
SR-15. The structure of the atom and the atomic nucleus.
TEST PAPERS
KR-1. Rectilinear uniformly accelerated motion.
KR-2. Newton's laws.
KR-3. The law of universal gravitation. body movement
around the circumference. Artificial satellites of the Earth.
KR-4. Law of conservation of momentum.
Law of energy conservation.
CR-5. Mechanical oscillations and waves.
CR-6. Electromagnetic field.
EXAMPLES OF SOLVING TYPICAL PROBLEMS
Laws of interaction and motion of bodies.
Mechanical oscillations and waves.
Electromagnetic field.
ANSWERS
Training tasks.
Tests for self-control.
Independent work.
Test papers.
Bibliography.

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There are various types of mechanical movement. Depending on the shape of the trajectory, the movement can be rectilinear or curvilinear. When moving, the speed of the body can remain constant or change over time. Depending on the nature of the change in speed, the movement will be uniform or uneven.

Rectilinear motion is a motion in which the trajectory of the body (points) is a straight line. For example, the movement of a car on a section of the road on which there are no ascents, descents, turns.

Uniform rectilinear motion is a motion in which the body travels the same paths for any equal intervals of time and the direction of motion does not change. I.

If we compare the uniform motion of several bodies, then it can be noted that the rate of change in their position in space can be different, which is characterized by a physical quantity called speed.

The speed of uniform rectilinear motion called the vector physical quantity, equal to the ratio of the movement of the body to the time during which this movement occurred.

(1)

The SI unit of speed is meter per second (1m/c). The unit of speed is taken to be the speed of such uniform motion, at which the body is 1 With makes a move 1 m.

In rectilinear uniform motion, the speed does not change with time.

Knowing the speed of uniform motion, you can find the movement of the body for any period of time:

(2)

With uniform rectilinear motion, the velocity and displacement vectors are directed in the same direction.

The main task of mechanics is to determine the position of the body at any time, that is, to determine its coordinates. The equation of motion is the dependence of the body coordinate on time for uniform rectilinear motion.

The body has moved . Let's direct the coordinate axis X in the direction of moving the body. x 0 is the initial coordinate of the body, x is the final coordinate of the body.

Thus, the coordinate of the body with uniform rectilinear motion at any time can be determined if its initial coordinate and the projection of the velocity of motion on the axis are known X. Velocity and displacement projections can be either positive or negative.

The graph of the dependence of the velocity vector module on time for uniform motion is a straight line parallel to the abscissa axis. Indeed, over time, the speed during such a movement remains constant.

Graph of body speed versus time for uniform motion V=const

With rectilinear uniform motion, the modulus of the displacement vector is numerically equal to the area under the displacement graph to the time axis.

The graph of the dependence of the movement of the body on time for a rectilinear uniform motion is a straight line passing through the origin. Moreover, the steeper the movement graph passes, the greater the speed of the body.

Graph of the path traveled by the body as a function of time

With rectilinear uniform motion, the modulus of the velocity vector is numerically equal to the tangent of the slope of the displacement graph to the time axis.

Since the dependence of the body coordinate on time is a linear function, the corresponding dependence graph (motion graph) is a straight line. An example of constructing such a graph is shown in the figure.

Graph of body coordinates versus time

TS -1 Rectilinear uniform motion.

Ioption.

1. A cyclist, moving uniformly, travels 20 m in 2 s. Calculate the distance it will cover when moving at the same speed in 10 s.

A. 60 m. B. 100 m. C. 150 m.

2
. The figure shows a graph of the dependence of the path when the cyclist moves on time. Determine from this graph the path that the cyclist traveled in the time interval from 1 to 4 s.

3. According to the schedule, determine the speed of the cyclist at the time t=2 s.

4
. The figure shows the graphs of the movement of three bodies. Which of these bodies is moving with the greatest modulo speed at the moment of time t=5 s?

5. According to the graph, determine the speed of the first body at the time t=5 s.

A. 2 s, 5 m.

B. 4 s, 10 m.

V. 5 s, 15 m.

7. Write down the equation of motion
second body on schedule.

AND.
.

B.
.

AT.
.

9. The boat is sailing against the current of the river. What is the speed of the boat relative to the shore if the speed of the boat relative to the water is 4 m/s and the speed of the river is 3 m/s?

A. 7 m/s. B. 5 m/s. B. 1 m/s.

10. The train traveled the first 40 km at a speed of 80 km/h, and the next 50 km at a speed of 100 km/h. Determine average speed trains all the way.

A. 95 km/h. B. 85 km/h. B. 90 km/h.

TS-1. Rectilinear uniform motion.

I
Ioption.

A car moving uniformly travels 50 m in 2 s. What distance will he travel in 20 seconds, moving at the same speed?

AND
. 500 m. W. 1000 m. W. 250 m.

2. Based on the path versus time graph, determine the path traveled by the body in a time interval of 3 to 5 s.

From the graph, determine the speed of the body at the time t=4 s.

4
. The figure shows the graphs of the movement of three bodies. Which of these bodies is moving at the lowest speed at the time t=2 s.

5. According to the motion schedule, determine the speed of the second body at the time 6 s.

6. According to the movement schedule, determine the time and place of the meeting of the first and second bodies.

A. 2 s, 10 m.

B. 1 s, 5 m.

7. Write down the equation of motion of the first body according to the graph.

AND.
.

B.
.

AT.
.

8. The movement of the body is described by the equation
. Which of the graphs shows the dependence of the coordinates of this body on time?

9. Subway escalator moves down at a speed of 0.7 m/s. What is the passenger's speed relative to the ground if he is going up at a speed of 0.7 m/s relative to the escalator?

A.0 m/s. B. 1.4 m/s. B. 1 m/s.

10. The car drove the first 20 km at a speed of 50 km/h, and the next 60 km at a speed of 100 km/h. Determine the average speed of the car for the entire journey.

A. 90 km/h. B. 80 km/h. B. 70 km/h.