The diagram shown in Figure 78. B2

The figure shows the change in air temperature over the course of three days. The date and time of the day are indicated horizontally, the temperature value in degrees Celsius is indicated vertically. Determine the difference between the largest and lowest temperature air 15 July. Give your answer in degrees Celsius.

It can be seen from the graph that on July 15 the highest temperature was 21°C and the lowest 8°C. And their difference is 13 °C.

Answer: 13.

Solution.
In order for the torque to be at least 120 N m, the engine revolutions per minute n must be at least 2000 and not more than 5000. Therefore, the desired minimum speed is determined by the formula v \u003d 0.036 2000 \u003d 72 km / h.

Answer: 72
3. The diagram shows the number of visitors to the RIA Novosti website for each hour on December 8, 2009. The number of the hour is indicated horizontally, the number of site visitors for a given hour is indicated vertically. Determine the difference between the largest and smallest number of visitors per hour on a given day from the diagram.

Solution.
It can be seen from the chart that the highest and lowest number of visitors were 80,000 and 10,000 respectively. Their difference: 70,000 people.

A1 A ball on a thread rotates in a circle with a radius of 15 m in a horizontal plane, making 100 revolutions in 90 s (Fig.). The path traveled by the ball during this time is approximately equal to 1) 628m 2) 15m 3) 94m 4) 85m

A2 The figure shows the forces acting on a material point. The modulus of the resultant force is equal to l)√l0H 2)4Н 3) 2√3 Н 4)2Н

A3 How will the friction force acting on a body moving on a horizontal rough surface change if its mass is increased by 3 times? 1) will increase by 3 times 2) will decrease by 3 times 3) will not change 4) will increase by 9 times

A4 How much greater is the water pressure at the tap on the first floor compared to the top floor of the house if the last floor is 40 m above the first? 1)400kPa 2)40kPa 3)25Pa 4)2.5Pa

A5 The spring pendulum consists of a spring and weight attached to it weighing 0.2 kg. In the equilibrium position, the load was given a speed of 2m/s. Kinetic energy load at this moment is 1) 0.8 J 2) 0.4 J 3) 0.1 J 4) 10 J

A6 The figure shows a photograph of the water surface along which the wave propagates from a shallower depth (lower part of the figure) to a greater one (upper part of the figure). The light stripes in the photo are the crests of the waves. With such a transition, the wave speed 1) decreases 2) increases 3) remains unchanged 4) the photograph does not allow comparing the wave speed

A7 The mass of 100 mol of gaseous nitrogen is 1) 50 kg 2) 2.8 kg 3) 1.4 kg 4) 7 kg

A8 The closed vessel contained vapors of the substance. The vessel was placed in the refrigerator. The figure shows a graph of the temperature T of a substance over time t. The energy given off by the substance is taken due to a decrease in the interaction energy of the molecules of the substance 1) in sections 1 and 2 2) in sections 2 and 3 3) in section 1 4) in section 2

A
9 Neon and argon of the same mass are in different vessels at atmospheric pressure. Under isobaric compression, the gases were cooled by 30ºС. The ratio of work done on gases А Ne /А Ar is equal to 1)1 2)2 3)1/2 4) √2

A10 On fig. shows a graph of the change in the temperature T of a substance over time t. At the initial moment of time, the substance was in a gaseous state. Which part of the graph corresponds to the cooling of the substance in the liquid state, and which part corresponds to its cooling in the solid state? 1) 2 and 4 2) 1 and 3 3) 1 and 5 4) 3 and 5

A11 The air gap between the plates of a flat capacitor was filled with mica, the dielectric constant of which is 6 times greater than the dielectric constant of air. The electric capacitance of the capacitor as a result of this 1) decreased by 6 times 2) did not change 3) increased by 6 times 4) increased by 36 times

A12 Two resistors with resistances R 1 \u003d 3 Ohms and R 2 \u003d 6 Ohms are connected in parallel in a DC circuit. What is the ratio Q 1 /Q 2 of the amount of heat released on these resistors in the same time? 1)1:1 2)1:2 3)2:1 4)4:1

A13 When an electric current with a force of 5A passes through the conductor for 2 minutes, work of 150 kJ is performed. What is the resistance of the conductor? 1) 0.02 ohm 2) 50 ohm 3) 3 k ohm 4) 15 k ohm

A14 The closed circuit is in a uniform magnetic field (Fig.). The circuit was turned counterclockwise by 90 ° around the axis OO", In this case, the magnetic flux through the surface of the circuit 1) increased by 2 times 2) decreased by 2 times 3) decreased to zero 4) did not change

A15 On fig. shows the change in the current I in the inductor from time t. The self-induction EMF module takes equal values in the time intervals 1) (0-1) s and (1-3) s 2) (3-4) s and (4-7) s 3) (1-3) s and (4-7) s 4) (0-1) s and (3-4) s

A16 A charged particle of mass m and charge q flies into a uniform magnetic field with induction B perpendicular to the lines of force with a speed v. The work done by the Lorentz force on the particle is 1)0 2)mυ2/2 3)2πqmυ2 4)2πqmυВ

A17 On the scale electromagnetic waves the range of visible light in the direction of increasing wavelength is followed by 1) ultraviolet radiation 2) x-ray radiation 3) radio waves 4) infrared radiation

A18 The image of the point S (see Fig.) obtained by a converging lens is the point: 1)1 2)2 3)3 4)4

A19 For the photoelectric effect, the statement is true:

electrons fly out from the surface of the body if the energy of the incident photons exceeds a certain value 2) electrons fly out from the surface of the body if the light intensity exceeds a certain value 3) electrons fly out from the surface of the body if this body is connected to a current source 4) electrons fly out from the surface of the body if the body temperature exceeds a certain value

A20 How does the total energy of several free resting protons and neutrons change as a result of their combination into an atomic nucleus? 1) increases if a radioactive nucleus is formed; 2) decreases if a stable nucleus is formed decreases with the formation of any nucleus 3) increases with the formation of any nucleus 4) does not change

A21 The figure shows the dependence of the projection of the force acting on a body with a mass of 1 kg, on time. The projection of the initial velocity of the body υ oh \u003d 1 m / s. By the end of the third second, the projection of the body's velocity is 1) 1m / s 2) -3m / s 3) 5m / s 4) 4m / s

A22 A person weighing 50 kg jumps onto a sled (sledge) weighing 200 kg from a height of 1 m on ice. The speed of the sleigh after the jump was 0.8 m/s. What is the horizontal component of human velocity? 1)1m/s 2)8m/s 3)6m/s 4)4m/s

A23 An ideal gas is contained in a vessel closed by a piston. The process of changing the state of the gas is shown in the diagram (see fig.). How did the volume of the gas change during its transition from state A to state B? 1) increased all the time 2) decreased all the time 3) first increased, then decreased

In which of the processes shown in the figure, carried out with a constant mass of an ideal gas, the temperature of the gas reaches the highest value? Curve 2-1-6 is described by the equation \(PV=const\). The figure given to the problem is shown on the right.

Task No. 4.3.40 from the "Collection of tasks for preparing for entrance exams in physics at USPTU"

The solution of the problem:

Let's think about where the highest temperature is reached on the PV diagram. To do this, take an arbitrary point A on this diagram (see the figure on the right) and write down the Clapeyron-Mendeleev equation:

\[(p_A)(V_A) = \frac(m)(M)R(T_A)\]

Let us express the temperature \(T_A\) from here:

\[(T_A) = \frac(((p_A)(V_A)))((\frac(m)(M)R)) = \frac(((p_A)(V_A)))((\nu R))\]

In the denominator of this expression, all quantities are constant. In the numerator we see the product \((p_A)(V_A)\). If we look at the graph, this product represents nothing more than the area of the shaded rectangle.

It turns out that on the PV diagram, the maximum temperature is reached at the point at which there will be the largest area of the rectangle formed by the coordinate axes and straight lines parallel to the same axes.

In our problem, points 2,3,4 and points 4,5,6 are located on the same straight line. This means that the highest temperature will take place at point 4, i.e. the highest temperature is reached in process 1-4.