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The nature test of the electric field force and the full analytic answer -32 are followed by the physics round of the college entrance exam in 2015

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The nature test of the electric field force and the full analytic answer -32 are followed by the physics round of the college entrance exam in 2015The nature test of the electric field force and the full analytic answer -32 are followed by the physics round of the college entrance exam in 2015 The nature test of the electric field force and the full analytic answer -32 are followed by the physics round ...

The nature test of the electric field force and the full analytic answer -32 are followed by the physics round of the college entrance exam in 2015
The nature test of the electric field force and the full analytic answer -32 are followed by the physics round of the college entrance exam in 2015 The nature test of the electric field force and the full analytic answer -32 are followed by the physics round of the college entrance exam in 2015 Zhang pei study planning system, share daily Use metal foil to make an uncharged ring and place it on a dry insulated table. Xiao Ming classmate made of insulating material the cap and the hair after friction, will the cap slowly close to the ring, downwards on cm ring were drawn to the cap on, as shown in figure, judgment and analysis of the above phenomenon, the following is true (), on the ring,,, were all at once the cap with the charge neutralization As shown here, the two positive charges of Q1 and Q2 are placed at point A and B, respectively. In L smooth for the diameter of the insulation on the half circle, wearing A charged ball + q (as A point charge), at point P balance, PA with an Angle of alpha AB, regardless of the small ball of gravity, () = = < Q2 [resolution] to choose A. The ball is in a state of equilibrium with three forces at P, FN and FN, which is perpendicular to the FB. It's the coulomb's law: you know, the tangent of alpha is equal to the solution, so A is wrong for B. So we know that the FA > FB, r1, > r2, so Q1 > Q2, so the field intensity of O is not zero, so C and D are both wrong. As shown in the picture, the two balls, both of which have A plus q and A minus q, are suspended by A thin wire, and the coulomb gravity is less than the ball's gravity. Now add a level and strong electric field to the right, again for the two balls to keep static state, the following conclusion is correct (),,,, the tension of AB is bigger than without the electric field [resolution] choose C, D. First, the overall balance analysis of AB is applied to the overall method, the tension of the suspension line is two m g, and the OA is in the vertical direction, and the choice C is correct. With B as the research object and then using the method of isolation analysis, partial suspension line AB to left, the tension for the electric field force and coulomb force and the force of gravity, is without the electric field, option D correct, so the answer for C and D. Use the holistic approach and the separation method to analyze the balance problem (1) as a whole, so that the force between this part becomes internal. If you think of A and B as A whole, the coulomb force and the elastic force between them are internal forces, so you can quickly judge the deflection of the fine line OA. (2) to analyze the effect of an object is to adopt an isolation method. For example, to analyze the deflection of fine line AB, select B or A to solve the equation. (3) the system balance problem can be solved by the same method if the direction of the electric field is tilted up or down. 【解析】(1)由小球运动到最高点可知,小球带正电 (2分)(2)设小 球运动到最高点时速度为v,对该过程由动能定理有,(qE-mg)L= ?(2 分)在最高点对小球由牛顿第二定律得, ?(2分)由??式解得, FT=15 N (1分)(3)小球在细线断裂后,在竖直方向的加速度设为a, 则 ?(2分)设小球在水平方向运动L的过程中,历时t,则L=vt ?(2 分)设竖直方向上的位移为x,则 ?(1分)由????解得x= m (2 分)所以小球距O点高度为x+L= m (1分)答案:(1)正电 (2)15 N (3) m The following three points: (1) A and B, when the two rings are falling, can analyze the force situation and the motion picture. (2) to correctly analyze the relationship between the linear velocity of the two loops in the semicircle. (3) the total applied kinetic energy theorem is applied to the velocity. [resolution] (1) for A and B ring as A whole by Newton's second law: ma, mg 2 + qE = 2 (2) A = solution. (1) isolation B ring and A rod for B ring down, the power of the size of F, have mg + F = ma - qE, (2) the acquired F = (1) (2) A ring when you arrive at the lowest point, triangle OAB is an equilateral triangle, as shown. A and B in the process of the system of center of gravity down (2 points) in this position, A and B along the direction at the same speed, so have vAcos alpha = vBcos beta, from the geometric knowledge knowable alpha beta = = 30 ?, So the vA = vB (2 points) according to the kinetic energy theorem 2 MGH ? 2 R + 2 qE - qE ? R = mv2 (4) solution to (1) answer: (1) (2) As shown in figure 1, two small spheres of charge with a + q are connected by a light string of light insulation with long l, resting on a smooth insulating surface. Student: the radius r of the two balls? L. K is the electrostatic constant. The light rope tension size is () a. 0. 2 B parsing 】 【 light rope tension size is equal to the coulombic force between two charged balls, F = by coulomb's law, option B is correct. 17, (2013 ? simulation of hongkou district) as shown in figure 3, point charge + 4 Q and + Q respectively fixed in A and B two points, two points C and D to match the AB trisection, now make A negatively charged particle from C point to A certain initial velocity movement to the right, regardless of the particle's gravity, then the particle motion velocity v between CD and the relationship between time t images may be in figure 4 (figure 3) figure 4 to parse choose BC particles in the AB balance in the middle of the line is the location of the field strength is zero, so = = x, namely, at point D particles in D point on the left side of the left in the electric field force, particles in point D on the right side to the right in the electric field force. So there are three things that happen in the motion of the particle: slow down to zero at the left of D and then accelerate to the left. When the particle can cross the D point, it's going to slow down on the left-hand side of D, and then accelerate after D. Or at the left of the D, the motion to D is zero, and then it is still, so the motion of the particle between the CD can be described by B and C, so BC is correct. 19, (as shown in figure 6) smooth thin rod with insulation level into A fixed Angle of theta, pole position is positively charged ball, quality as the m, charge for q, to make the ball stationary on the pole, can add A strong electric field and applied electric field strength to meet what condition, the ball can remain still on rod () a. perpendicular to the inclined upward, field size of b. vertical upward, field size for c. perpendicular to the inclined upward, field size for d. level, to the right field size to figure 6 [resolution] choose B if the applied field strength of electric field is perpendicular to the inclined upward, the ball bearing analysis shows that it had been hit by a vertical downward gravity, perpendicular to the inclined upward in the electric field force and vertical to the direction of the rod support, in under the action of the three forces, direction along the bar could not balance, option AC error; If the applied electric field strength of the vertical upward, the ball bearing analysis shows that when E = big reverse, like electric field force and gravity ball can remain still on pole, option B correct; So if the electric field is going to be equal to the force of the field force Eq = mgtan theta, the ball is in equilibrium, E =, so D error. If A and B are charged by the same charge, the ball is affected by coulomb repulsion, which must be made to increase the curve motion of the reduced acceleration. If B is negatively charged, then B goes to a higher position. If A and B have A different charge, the ball of B could do A uniform circular motion around A ball, which is A curve that does the same thing as the velocity and the magnitude of the acceleration, and that's the right choice. As shown in figure 10, there are four balls on the horizontal surface of the smooth insulation, with the power of -q, q, -q, and q. The four balls form a diamond, and the Angle between the link of -q and q is alpha. If the system is in a state of balance, the correct relation may be () A.c os3 alpha = biggest os3 alpha c.s. in3 alpha = = D.s in3 alpha = in figure 10 Zhang pei learning planning system is an effective way to improve the academic performance of the system. Can help students in method, plan Content, learning solution integration and distribution, effectively improve academic performance.
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