In the inertial frame of reference, the bar begins to slide.
Theory: If the sum of all forces is not zero, then the body will move with acceleration.
Newton's second law: The acceleration of a body is directly proportional to the resultant of all forces, and inversely proportional to its mass.
Acceleration is directed in the same direction as the resultant of all forces. Fa
The resultant of all forces is found by the formula: F = ma
Body weight- the force with which the body acts on the fulcrum or suspension point.
In the inertial system, the weight of the body is equal to the force of gravity P = F heavy = mg. In the case of a non-inertial system, for example, in an elevator, when the elevator moves vertically up (down) with acceleration, the body weight increases (decreases) P = m (g ± a).
Exercise: What is the work of the traction force acting on a car with a mass of 20 tons, if, having started to move from a state of rest with a constant acceleration of 3 m / s 2, the car has covered a distance of 100 m? Friction is neglected.
The task will solve the exam: In the inertial frame of reference, the bar from the state of rest begins to slide with acceleration downward along inclined plane... The resultant of all forces acting on the bar is co-directed to the vector 
1) 1
2) 2
3) 3
4) 4
Solution: Acceleration is directed in the same direction as the resultant of all forces. Fa, the bar slides with acceleration down the ramp.
Answer: 2
The task will solve the exam: One and the same horizontal force F acts first on body 1 with a mass of 0.5 kg, and then on body 2 with a mass of 3 kg. Before the start of the force, both bodies rested on a smooth horizontal table. With what modulus of acceleration will body 2 move under the action of force F, if body 1 moves with acceleration, the modulus of which is 1.8 m / s 2?
1) 0
2) 0.3 m / s 2
3) 0.6 m / s 2
4) 0.9 m / s 2
Solution: 1 way. We find the force F = m 1 a 1 = 0.5 · 1.8 = 0.9 N. Then we calculate the acceleration of 2 bodies a 2 = F / m 2 = 0.9 / 3 = 0.3 m / s 2
Method 2. The mass is 6 times more, since the forces are equal, then the acceleration is 6 times less.
Answer: 2
The task will solve the exam: In the inertial frame of reference, the bar begins to slide with acceleration down the inclined plane. The modulus of the resultant forces acting on the bar is equal to 
1) mg
2) ma
3) F tr
4) N
Solution: The modulus of the resultant forces F = ma according to Newton's second law.
Answer: 2
Physics oge assignment: A bar weighing 200 g, suspended on a light spring, is lifted upwards with an acceleration equal to 0.5 m / s 2 in modulus and directed upwards. What is the modulus of elasticity of the spring?
Solution: During lifting, the elastic force is equal to the weight of the body, the body moves upward with acceleration, the weight of the body is found by the formula: P = m (g + a), we get F control = m (g + a) = 0.2 (10 + 0, 5) = 2.1 N.
Answer: 2.1 N
Oge assignment in physics (fipi): A body weighing 6 kg moves along the OX axis of the inertial reference system. The table shows the dependence of the projection of the velocity υ х of this body on the OX axis on time t. What is the projection on the OX axis of the force acting on the body?
Solution: the table shows that the body is moving uniformly, we find the acceleration by the formula: a = (υ-υ 0) / t = (1.5-0) / 3 = 0.5 m / s 2 using Newton's second law, we calculate the force acting on a body weighing 6 kg. F = ma = 6 0.5 = 3 N.
Answer: 3 N
Exercise demo version OGE 2019: At the moment t = 0, two horizontal forces begin to act on a body at rest on a smooth horizontal plane (see figure). Determine how the body's velocity module and the body's module of acceleration then change over time. 
For each value, determine the corresponding change pattern:
1) increases
2) decreases
3) does not change
Write down the selected numbers for each physical quantity... The numbers in the answer may be repeated.
Solution: Forces are directed along one straight line in opposite directions. The resulting forces F = F 2 -F 1 = 2.5-1 = 1.5 N. is not equal to zero, therefore the body will move uniformly a = const (since the equal force of the forces is constant). Therefore, the speed of the body will increase.
When completing tasks 2-5, 8, 11-14, 17-18 and 20-21 in the answer field, write down one number that corresponds to the number of the correct answer. The answer to tasks 1, 6, 9, 15, 19 is a sequence of numbers. Write down this sequence of numbers. Write down the answers to tasks 7, 10 and 16 as a number, taking into account the units indicated in the answer.
1
Establish a correspondence between physical quantities and the units of measurement of these quantities in the SI system.
2
In the inertial frame of reference, a bar of mass m begins to slide with acceleration down an inclined plane (see figure). The modulus of the resultant forces acting on the bar is equal to
3
The sled is moving down the hill from a state of rest. Friction is negligible. The dependence of the kinetic energy of the sled on time corresponds to the graph
4
If you use a fixed block, then
1) you can get a win only in strength
2) you can get a win only in work
3) you can get a gain both in strength and in work
4) you cannot get a gain either in strength or in work
5
Compare the fluid pressure on the balls shown in the figure
1) p 1 = p 3< p 2
2) p 2> p 3 = p 1
3) p 3> p 1> p 2
4) p 3< p 1 < p 2
6
The parachutist descends evenly to the surface of the Earth. How does this change kinetic energy a parachutist and his potential energy relative to the Earth?
For each value, determine the corresponding change pattern:
1) increases
2) decreases
3) does not change
7
Under the action of a force of 20 N, a weight of 2 kg moves up an inclined plane (friction is negligible). The efficiency of the inclined plane is 50%. What is the length of the inclined plane if its height is 1 m?
Answer: _____ m.
8
Which statement is (are) true?
A. Only repulsive forces act between molecules in a liquid.
B. Liquid molecules move continuously and chaotically.
1) only A
2) only B
3) both statements are true
4) both statements are wrong
9
The figure shows a graph of body temperature versus time. Initially, the substance was in a liquid state. Using the data of the graph, select from the proposed list two correct statements and write down the numbers under which they are indicated in the answer.
1) Point B corresponds to the solid state of the substance
2) The line of the GD graph corresponds to the process of heating a substance in a liquid state
3) The BV line of the graph corresponds to the crystallization process of the substance
4) The temperature of the substance in the states represented by points B and D is the same
5) The specific heat capacity of a substance in the liquid state is equal to its specific heat capacity in the solid state
10
How much heat is required to boil 2 liters of water in a 400 g electric steel kettle? The initial temperature of the water and the kettle is 25 ° C. Specific heat steel 500 J / (kg * deg).
Answer: ______ kJ.
11
The sign of the excess charge that bodies receive during friction depends on the binding energy of the electron with the atoms of the substances from which the bodies are made. The lower the binding energy, the easier the substance gives up its electrons. The diagram shows a number of substances in ascending order (from top to bottom) of the binding energy of the electron with the atoms of the substance.
According to the considered model of electrification when rubbing a stick made of wood against a piece of silk.
1) wood and silk get a positive charge
2) wood and silk get a negative charge
3) wood gets a negative charge, and silk gets a positive charge
4) wood gets a positive charge, and silk gets a negative charge
12
The figure shows a section of a DC circuit containing five identical resistors of 4 ohms each. The ammeter shows a current of 1 A.
Determine the total electrical resistance of the circuit section and the voltmeter reading. Ammeter and voltmeter are considered ideal.
1) 14 Ohm, 2 V
2) 14 Ohm, 4 V
3) 20 Ohm, 2 V
4) 20 Ohm, 4 V
13
A magnet is introduced into a coil closed to a galvanometer. The direction of the induction current depends
A. on whether a magnet is inserted into or removed from the coil
B. from which pole the magnet is inserted into the coil
The correct answer is
1) only A
2) only B
4) neither A nor B
14
In which of the cases described below, the radiation occurs electromagnetic waves?
1) Direct current flows through the conductor.
2) A permanent magnet is introduced into the coil.
3) A discharge occurs between the poles of the electrophoretic machine.
4) Rub the ebony stick on the fur.
15
Due to friction against silk, the glass ruler acquired a positive charge. How did the number of charged particles on the ruler and silk change? Consider that there was no exchange of atoms between the ruler and silk during friction.
For each physical quantity, determine the corresponding nature of the change:
1) increased
2) decreased
3) has not changed
Write down the selected numbers for each physical quantity. The numbers in the answer may be repeated.
16
In the electrical circuit shown in the diagram, the resistances of the conductors are equal to R 1 = 10 ohms and R 2 = 5 ohms, respectively. The second voltmeter shows a voltage of 8 V. What is the reading of the first voltmeter? Voltmeters are considered ideal.
Answer: _____ B
17
How many α- and electronic β-decays must the uranium 234 92 U nucleus undergo to turn into a uranium nucleus
1) one α- and two β-decays
2) two α- and one β-decays
3) two α- and two β-decays
4) one α- and one β-decay
18
The figure shows an experiment on observing the reflection and refraction of a light beam at the air-glass interface.
In the figure, the numbers indicate respectively
1) 2 - incident ray, 3 - reflected ray, 1 - refracted ray
2) 2 - incident ray, 1 - reflected ray, 3 - refracted ray
3) 1 - incident ray, 2 - reflected ray, 3 - refracted ray
4) 1 - incident ray, 2 - reflected ray, 3 - refracted ray
19
After analyzing the graph of the dependence of the coordinates of the oscillating body on time, select from the proposed list two correct statements and enter them into the table of answers.
1) The period of oscillation of the body is 0.8 s.
2) The vibration amplitude is 8 cm.
3) The oscillation frequency is 25 Hz.
4) The vibration amplitude is 4 cm.
5) The period of oscillation of the body is 0.4 s.
Read the text and complete assignments 20–22.
Moon nature
The moon is natural satellite Earth. It is practically devoid of atmosphere. So, its mass and dimensions are small, but already at a speed of 2.38 km / s, gas molecules are able to leave it. Therefore, on the lunar surface there is not and cannot be water in a liquid state: evaporating, it would form a gas envelope around the Moon, which would quickly dissipate. However, recent studies have shown the existence of water reserves in the form of ice in the polar regions of our satellite.
The sky of the moon is black due to the lack of atmosphere, and even during the day you can observe the stars and planets. The decoration of the lunar sky is our Earth, the disk of which is 3.5 times larger than the solar disk. The absence of an atmosphere leads to sharp fluctuations in the temperature of the lunar surface during the lunar day: during the day the temperature reaches 130 ° С, and at night up to -170 ° С. Note that the day and night on the Moon last about 2 weeks, since the Moon makes one revolution around its axis in 27.3 Earth days.
Even naked eye it can be seen that the surface of the moon is heterogeneous: the dark areas were called seas (Sea of Rains, Sea of Clarity, Ocean of Storms, etc.), light areas were called continents. These names have survived since the 17th century, when scientists hoped that the moon had liquid water. Characteristic feature lunar relief are craters - ring structures, in the center of which there is a small hill. Most of the craters were formed as a result of meteorites falling on the Moon, which, when they hit the lunar soil, collapsed, causing a shock wave in the lunar surface and an elevation in the center of the fall. The largest craters are named after the great astronomers: Tycho, Kepler and Copernicus.
Samples of lunar rocks were brought to Earth thanks to successful manned flights to the Moon. They include chemical elements well-known on Earth: Si, Al, Fe, Ca, Mg and others. But lunar rocks contain more refractory chemical elements: Ti, Zc, Cr and a smaller number of low-melting: Pb, K, Na. Due to the lack of water on the moon, minerals on it are much less than on Earth. No microorganisms were found on the Moon.
20
Why on the Moon and other satellites of the planets, craters from meteorite impacts persist for billions of years, but on Earth they are almost gone?
1) small force of gravity compared to the earth
2) different illumination of these objects by the Sun
3) lack of atmosphere and atmospheric phenomena
4) various chemical composition
21
Why is there not a drop of water in the lunar seas? Which statement (s) is true?
A. Water in Solar system exists only on planet Earth.
B. Liquid water evaporates quickly.
1) only A
2) only B
4) neither A nor B
Part 2.
When performing task 22 with a detailed answer, first write down the task number, and then the answer to it. A complete answer should include not only the answer to the question, but also its detailed, logically coherent rationale.
Describe the necessary initial conditions for the creation of the first human settlement on the moon.
Show Answer
The moon is a natural satellite of the earth. It is practically devoid of atmosphere. For human life, an atmosphere is needed. No microorganisms were found on the Moon. Needs microorganisms, the emergence of flora and fauna. On the lunar surface there is not and cannot be water in a liquid state: evaporating, it would form a gaseous envelope around the Moon, which would quickly dissipate. However, recent studies have shown the existence of water reserves in the form of ice in the polar regions of our satellite.