14. It is reported that the first "livable" planet was recently discovered outside the solar system, and its mass is about 6.4 times that of the Earth. A person who weighs 600N on the surface of the earth will weigh 960N on the surface of the earth. It can be inferred that the ratio of planet radius to radius of the earth is about ().
a、0.5 B、2 C、3.2 D、4
15. A series of harmonic shear waves propagate along the negative direction of the X axis, with the wave velocity of v = 4m/s. The vibration image of the particle at the known coordinate origin (x=0) is shown in Figure (a), and the figure that can correctly represent the waveform at t=0. 15s in the following four figures is ().
16. As shown in the figure, a piston with a mass of m seals a certain mass of gas in the cylinder, and there is no friction between the piston and the cylinder. State A is the equilibrium state of gas when the steel cylinder is placed in the ice-water mixture, and State B is the equilibrium state when the steel cylinder is taken out of the container at room temperature (270℃). During the change of gas from state A to state B, the atmospheric pressure remains unchanged. If the potential energy between gas molecules is ignored, the following statement is correct ()
A, compared with state B, gas molecules in state A hit the piston more times per unit time.
B, compared with state A, the gas molecules in state B have greater impulse on the piston per unit time.
C, at the same time, the gas molecules in state A and state B have the same impulse to the piston.
D from state a to state b, the internal energy of the gas increases, the outside does work on the gas, and the gas releases heat to the outside.
17. There is an inverted glass cone on the desktop, and its vertex just touches the desktop. The axis of the cone (dotted line in the figure) is perpendicular to the desktop, and the section passing through the axis is an equilateral triangle, as shown in the figure. There is a cylindrical parallel beam with radius r vertically incident on the ground of the cone, and the central axis of the beam coincides with the axis of the cone. It is known that the refractive index of glass is 1.5, and the radius of the spot formed by the light beam on the desktop is ().
a、r B、 1.5r C、2r D、2.5r
18. As shown in the figure, there is an object with a mass of m on a sufficiently long inclined plane with an inclination of 300, and a force F acts along the inclined plane. The force f can change with time in four ways as shown in Figures (a), (b), (c) and (d) (in the figure, the ordinate is the ratio of f to mg, and the force is positive upward along the inclined plane).
It is known that the velocity of this object is zero when t=0. If v 1, v2, v3 and v4 are used to represent the velocity of an object at the end of 3 seconds under the action of the above four forces, the largest of these four velocities is ().
a、v 1 B、v2 C、v3 D、v4
19. A large number of ground hydrogen atoms were bombarded by a large number of electrons with certain capabilities, and a certain number of spectral lines were observed. The ability to adjust electrons is observed here, and it is found that the number of spectral lines has increased by five. Δ n represents the difference of the highest excited quantum number n observed on both sides, and e represents the energy of the electron after height adjustment. From the energy level diagram of hydrogen atom, the possible values of △n and e are ().
a、△n= 1， 13.22 eV & lt； E< 13.32 ev
b、△n = 2 13.22 eV & lt； E< 13.32 ev
c、△n= 1， 12.75 eV & lt； E< 13.06 ev
d、△n = 2 12.75 eV & lt； E< 13.06 ev
20.a, B, C and D are four points in a uniform electric field, which are exactly four vertices of a rectangle. The electric field lines are parallel to the rectangular plane. It is known that the potential at point A is 20V, that at point B is 24V, and that at point D is 4V, as shown in the figure. Therefore, the potential at point C is ()
a，4V B，8V C， 12V D，24V2 1。 As shown in the figure, LOO'L is a broken line, and its two angles ∠LOO' and ∠OO'L' are both 450. There is a uniform magnetic field on the right side of the dotted line, which is perpendicular to the OO' direction and moves in a straight line at a uniform speed, just at the position shown in the diagram at time t=0. Taking the counterclockwise direction as the positive direction of the current in the lead frame, in the following four pictures, the current-time (I-t) relationship can be correctly expressed (time is in l/v) () Non-multiple choice question *** 10, and the score is *** 174.
22.( 17 points)
Experimental questions:
(1) Observe the sinusoidal voltage signal with the frequency of 900Hz with an oscilloscope. Connect the signal to the Y input of the oscilloscope.
○ 1 When the waveform as shown in figure 1 appears on the screen, adjust the button. If the positive and negative half cycles of the sine wave are out of the range of the screen, you should adjust the button or the button, or use both buttons at the same time to make the whole waveform of the sine wave appear on the screen.
○2 If a complete sine wave just appears on the screen, put the button in place and then adjust the button.
(2) The collision recovery coefficient is defined as, where v 10 and v20 are the velocities of the two objects before the collision, and v 1 and v2 are the velocities of the two objects after the collision. The recovery coefficient of elastic collision e= 1, and e
Install the experimental device, make preparations before measurement, and write down the position indicated by the heavy hammer line.
Step 1, let the ball 1 roll down from point A on the slide and fall to the ground. Do not release the ball 2. Repeat it many times to enclose the ball's landing point into a circle as small as possible, and its center is the average position of the ball's landing point.
Step 2, put the ball 2 at point C on the front edge of the chute, let the ball 1 roll down from point A, and let them collide. Repeat it many times and mark the average position of the ball after collision in the same way as in the first step.
Step 3, measure the distance from the average position of the three falling points to the O point with a scale, that is, the length of the line segments OM, OP and on.
In the above experiment,
○ 1P point is the average position,
M point is the average position,
N points are the average positions.
○2 Please write the principle of this experiment and the expression of the recovery coefficient expressed by the measured value.
○3 Are the distances OM, OP and ON between the three landing points and the O point related to the quality of the experimental ball?
.
23.( 15) Athletes A and B found that after short-distance acceleration, A could run the whole course at a speed of 9m/s; B The movement from starting to receiving the stick is accelerated at a constant speed. In order to determine the start time of B, it is necessary to set a sign at a proper position in front of the relay area. In an exercise, A marked the relay area in front of S0= 13.5m, and gave a starting password to B when running to this mark at the speed of V = 9m/s. B started after hearing the password at the front end of the relay area, and was caught up by A just when the speed reached the same as A, completing the handover stick. It is known that the length of the relay area is L=20m.
Q: (1) The acceleration a of B before connecting the stick in this exercise;
(2) The distance from B to the end of the relay area when completing the handover bar. 24. As shown in the figure, a ball made of insulating material with mass m and a metal ball with mass M= 19m are hung side by side. Now the insulating ball is pulled to the position of θ = 600 with the vertical direction and released freely, and then it collides with the metal ball elastically at the lowest point. There is a magnetic field perpendicular to the paper near the equilibrium position. It is known that due to the damping effect of the magnetic field, the metal ball will stop at the lowest point before colliding again. The maximum angle of the insulating ball deviating from the vertical direction after several collisions will be less than 450.
25. The fluorescent screens of the two screens are placed perpendicular to each other. In the two screens, the straight lines perpendicular to the intersection of the two screens are the X axis and the Y axis, and the intersection O is the origin, as shown in the figure. At y & gt0，0 & lt； There is a uniform magnetic field perpendicular to the paper in the area of x<a, and it has a uniform magnetic field perpendicular to the paper in the area of Y >: 0 and x>A. The magnetic induction intensity in both areas is B, and there is a small hole in the point of O, with the mass of beam A being m and the charged amount being Q (Q >). 0) Particles inject a magnetic field along the X-axis through the small holes, and finally hit the vertical and horizontal fluorescent screens to make them glow. The velocity of incident particles can take different values from zero to a certain maximum. It is known that the particle with the maximum velocity is at 0.
2007 National Science Comprehensive Volume 1 Answer Analysis
14: b analysis: g'= 1.6g can be obtained from the meaning of the question; By replacing GM=gR2 with gold, we can get the solution R'=2R.
15: A analysis: the particle at the origin moves downward on the positive semi-axis of y according to the vibration image, and only the A option is correct because it propagates to the negative X axis.
16: AC analysis: due to the equal pressure in the two States, the total impulse of gas molecules to the piston in unit time and unit area must be equal; Because the temperature of state B is higher than that of state A, the average momentum of molecules increases, and because the total impulse is unchanged, the number of molecules rushing to the piston in state B per unit time is definitely less than that in state A. 。
17: C analysis: As shown in the figure, when the light hits A or B, the incident angle is greater than the critical angle and total reflection occurs. Then it is concluded from the geometric relationship that when the light reaches the interface for the second time, it is vertical. What is o'clock? The center of gravity of ABC, let EC=x, is obtained from the geometric relationship:. Solve the spot radius x=2r.
18: C analysis, choose downward as the positive direction, and get the result of Figure A:
For chart b:
For chart c:
For diagram d:
Combine the four options to get the maximum value.
19: AD analysis: there are two possibilities. The first one is n=2 to n=4. Because it is electron bombardment, the energy of electrons must satisfy 13.6-0.85.
20: B analysis: Using a conclusion: In a uniform electric field, the potential difference between two equidistant points in any family of parallel lines is equal, so Uab=Ucd, so the potential at point C is 8V; 2 1: D analysis: according to the initial position, the effective length of cutting is gradually increasing, and it is counterclockwise, so choose a BD. Because the second second of BD is the same, there is no difference. In the third second, a part of the wireframe has been separated from the upper magnetic field, and the effective length of cutting is decreasing, and it is clockwise, so only the D option is correct.
② scanning range 1k gear scanning fine adjustment
(2) ① Point P is the average position of the ball 1 in the first step of the experiment.
The point m is the average position of the ball 1 after hitting the ball 2 1 landing point.
N point is the average position where the ball 2 falls.
(2) After the ball flies out of the notch C, it takes the same time to do the flat throwing action. Suppose t, there is
The ball 2 is at rest before the collision, that is to say
(3) OP has nothing to do with the mass of the ball, while OM and ON have something to do with the small mass. 23. Solution: (1) Let the elapsed time t, if A catches up with B, there will be vt-vt/2= 13.5 according to the meaning of the question.
Substituting v=9 gives: t=3s,
Then v=at
Solution: a=3m/s2
(2) When catching up with B, B walked the distance of S,
So: s=at2/2
Substitute the data to get s =13.5m.
So what is the distance from B to the end of the relay area? S = 20- 13.5 = 6.5m24. Solution: Let the cycloid length of the ball m be L.
Ball M meets the conservation of mechanical energy before colliding with M in the falling process: ①
The collision process between M and M meets the following requirements: ②
③
At the same time, ② ③ get: ④
Explain that the ball bounced, and then the ball collided with the ball M at the speed of bouncing, satisfying:
⑤
⑥
Solution: ⑦
Finishing: 8
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The critical speed with a deviation direction of 450 satisfies: ⑩.
At the same time, ① ⑨ ⑩ Substituting data, when n=2,
When n=3,
Therefore, the maximum collision time is 3 times. 25 solution: The critical condition of the screen bright line range on the Y axis is shown in figure 1: The trajectory of charged particles is tangent to x=a, where r=a and the highest point on the Y axis is y = 2r = 2a.
The critical condition of the screen bright line range on the X-axis is shown in Figure 2: the limit of the left boundary is still tangent to x = 2a, and the trajectory of the charged particles on the right is a circle. According to the geometric knowledge, the particle with the highest speed on the X-axis is a solid line, as shown in Figure 2, which consists of two arcs with the centers of C and C'. C' is derived from symmetry. On the X axis, it is set in the left and right magnetic fields, and the movement time is t 1 and t2 respectively, which meets the following requirements.
Obtaining solutions from mathematical relations;
Substitute the data to get:
So the range on the x axis is