Physics question 19, please help solve it

d, because the volume of the gas has become smaller.

First of all, because the tensile force on both sides of the pulley is equal in magnitude and = ga (gravitational force of a).

The force balance analysis of b shows that 2sin *ga=gb, ga and gb are fixed values, so sin is also a fixed value, so the magnitude does not change, because it moves from q to p, it does not change, so a rises

The tensile force on the rope is equal to the gravitational force of B, which is a constant force, and the gravitational force of A is also unchanged, and the ropes on both sides of the pulley connected by A are symmetrical, so the angle is unchanged, and A rises.

According to the balance of forces, draw a diagram and you will know the result.

Otherwise, it won't be balanced.

Conservation of momentum problem.

The original question is incorrect, and according to the answer, the question should be corrected to read: "A sandbag of mass m is thrown at ship B from ship A at a rate of v relative to ship A".

Solution] The direction of the initial velocity v of the first ship is taken as the positive direction, and the velocity of the sandbag is taken as a negative value when the ground reference frame is uniformly selected.

Before the sandbag is thrown, the total momentum of the sandbag and the boat is mv

After the sandbag is thrown, the momentum of ship A is (m-m)v A, and the momentum of the sandbag is m(v A-v) According to the law of conservation of momentum, there is:

mv = (m-m)v a, m(va-v).

v A = (mv + mv) m

Taking the sandbag and the B boat as the research objects, according to the law of conservation of momentum, there are:

mv m(v a-v) (m+m)v b.

v B = (m + m )v [m(m+m)]= (m +mm + m -mm)v [m(m+m)]=[m(m+m)-m(m-m)]v [m(m+m)]=v- m(m-m)]v [m(m+m)] exactly matches the answer you provided, indicating that the original question is wrong.

First of all, the speed of throwing the sandbag is -v, pay attention to the rate is v, but the direction is opposite, otherwise it will not be able to throw the ship B.

Therefore, mv=-mv+(m-m)(vA), and vA=(mv+mv) (m-m).

And ship B mv+(-mv)=(m+m)(vB), we get vB=(mv-mv) (m+m).

What I have in mind is to use the conservation of momentum to solve the problem, and the result is different from yours.

Second=210mms=

2: According to the law of uniform acceleration motion: from the beginning of rest, the ratio of the distance passed in an equal time interval is the ratio of the consecutive odd number 1:

9...It can be deduced according to the formula of s=1 2at 2, and you can also draw a speed time graph, and you can reason about it yourself, and the memory will be profound, don't be lazy. ab distance:

Distance between the last two points =: 97; It can be seen that point A is point 11, point B is point 12, followed by point 49 and point 50, respectively. There are 13 48 missing paper segments in the middle, for a total of 36 points;

3: In the same way, the distance between point 1 and point 2 is, according to the formula s=1 2at 2, a=1m s 2.

1.v= t1= v2= (points The third question is not difficult, you can write it yourself.

First of all, the mechanical energy of water is definitely not conserved, because in the process of falling wooden blocks, the water is rising, the gravitational potential energy must increase, and the mechanical energy increases.

How much to increase is key.

The wooden block will not sink out of thin air, it is to use external force to make the sinking, the buoyancy of the wooden block in the process of immersion in the water gradually increases, the buoyancy of the wooden block completely invading the water is 2mg, the buoyancy of this process gradually increases from mg to 2mg, so the external force is applied in two processes, gradually increasing from 0 to mg, until it is completely immersed in water, the external force increases to mg and remains unchanged.

The work done by the gravity of the wooden block itself wg=mg(h-a2).

The average force magnitude of the first process of external force is: mg 2, and the displacement s1=a 2 in the direction of the force

The first process does work w1 = mg 2 * a 2 = mga 4

The magnitude of the external force in the second process is: mg, the displacement s2=h-a in the direction of the force, and the work w2=mg(h-a).

According to the conservation of energy: wg + w1 + w2 = 2mg (h-5 8a), this is the gravitational potential energy acquired by water.

The wooden block slows down to the end, does not gain any energy, and the sum of the work done by gravity and external forces is 2mg (h-5 8a), which is converted to the gravitational potential energy of water.

You can also do buoyancy to understand that the whole process of the wooden block has been overcoming buoyancy to do work, overcoming buoyancy to do work into the mechanical energy of water, buoyancy work is divided into two processes, the first process of buoyancy gradually increases, the second process of buoyancy remains constant 2mg

The magnitude of buoyancy gradually increases from mg to 2mg, the average buoyancy of this process is 3 2mg, and the displacement is: a 2

The work done by buoyancy in this process is w1=3mga 4

The work done by buoyancy in the second process is w2=2mg(h-a).

The sum of the two w1+w2=2mg(h-5a8) is the increased mechanical energy of water.

It's very tangled, I don't know if it's wrong, and enthusiastic netizens are welcome to correct.

Because the wooden block is at the bottom of the pool, the center of mass has not arrived, and the center of mass is at the midpoint, so it is H-A 2

In fact, the "right" answer is also wrong.

Second, when the slide is shifted to the right, the resistance of the loop becomes larger, and therefore the current in the two solenoids becomes smaller.

Finally, according to Lenz's law, the wireframe should have a tendency to hinder the decrease of magnetic flux, and in order to achieve this, the effective area of the wireframe needs to be increased (i.e., the magnetic field lines should be perpendicular to the wireframe plane as much as possible), so the wireframe needs to rotate clockwise.

Or if you feel that it is not rigorous enough to get this conclusion directly according to Lenz's law, you can assume the positive and negative directions of the power supply, analyze the direction of the induced current generated in the wire frame respectively, and then judge the force, and finally determine the direction of rotation, and you will find that it has nothing to do with the positive and negative direction of the power supply.

d Because the magnetic field passing through the coil changes.

The purpose of the plane mirror is only to reflect light, so you can use the mirror method to move the north wall behind the plane mirror. So that the person is on the left side of the mirror, and the wall is on the right side of the mirror. The wall is infinitely large, and one can only see where the mirror can reflect to the human eye.

Therefore, in the straight line from the human eye to the mirror image of the wall, only those who pass through the mirror can be seen.

The mirror has a radius of only 10cm, and the mirror image of the mirror is distance from the mirror, and the radius of the visible area on the wall can be obtained from the proportional relationship is r=10*5

The area of the circle is:

The answer to the seventh question is: 15km... 3600mm。。。1800dm。。。120min=2h

The answer to the eleventh question is: dm. min 。。nm 。。cm 。。cm 。。s

The answer to question 12 is: cm... s。。。

Please reply if you still need it.

There is no diagram, it can only be imagined out of thin air.

After the object is completely submerged in water, the buoyancy experienced is 10 - 3 = 7nThe volume of the discharged water is 500 - 400 + vacant volume = 100+x ml

The conditions are insufficient, and it is impossible to do it without a diagram.