Physics questions are asked for answers, and physics questions continue to be asked

Hello! A force that produces the same effect as several forces acting together is called the resultant force of several forces.

Make a parallelogram with a directed line segment representing two common point forces as the adjacent edges, and the diagonal line between the two adjacent edges represents the magnitude and direction of the resultant force of the two forces

Choosing d is to use the parallelogram rule to solve the resultant force expectancy.

This question is much simpler because the premise is already limited to "two forces on the same straight line", you should be a junior high school student, right?

The resultant force, as the name suggests, is the "combined" of several forces. However, it is not a random synthesis, and it must be based on the fact that the original forces have the same effect as the "resultant force" of these forces, that is, equivalent substitution.

An example might be better understood. You go to the store to buy a 10 yuan item, and when you pay, you can give the cashier 2 yuan first, and then 8 yuan to the cashier; You can also give 10 yuan directly to the cashier. Among them, 2 yuan and 8 yuan are "components", and 10 yuan is "resultant force".

In junior high school, since only linear motion is contacted, the component force and the resultant force can be approximated and solved according to the arithmetic method. However, in high school, due to the introduction of the concept of "vector" and the generalization of the motion of objects, it is no longer possible to approximate the solution by arithmetic, but to follow the general calculation rule of vectors, the "parallelogram rule".

If you understand the concept of resultant force and component force, let's go back to the topic. Since the two forces of the object have been restricted to be collinear in the problem, the larger force can be directly subtracted from the smaller force to obtain the magnitude of the resultant force, and the direction of the resultant force is consistent with the direction of the larger force. So A is false, B is correct, C is correct, and D is wrong.

The resultant force of b and c refers to the vector sum of multiple forces acting on the same object. The resultant force is a vector quantity.

If, f1=f2, and the direction is the same, it is still considered to be two forces. Instead, choose B.

t when f=0 times get t=3 10 -5s

At this time, f is taken as the average value and substituted in:

p=6×10^-3

3.According to the momentum theorem, it can be seen that

m=2×10^-5kg

1. Choose C, the bicycle is going forward.

The spokes of the upper half are forward relative to the bike, so its total speed is his speed plus the speed of the bike.

The lower half of the spoke is backwards relative to the bike, so its total velocity is his speed minus the bike's speed.

Therefore, the speed of the lower half is smaller than the speed of the upper part, and it is easier to see 2, whether it rains or not, it is flat, thinking that it is the amount of precipitation, and the ground is used as a reference, It is to measure the height of the water above the ground, so it is necessary to be level with the ground, and the third empty fill is more, and you can understand it by looking at the map!

The above question is a headache, so I'll talk about the addition.

The formula you substitute, the answer you get is that the quantity introduced in high school is called displacement, which is positive and negative and has different directions. So the answer is the same as you might think, find a stop.

This question is selected by student A, this kind of question, you must first understand two questions.

First: In the image of the s-t function, the slope of a point in the image is the velocity of that point.

Second: distinguish the trend of movement, which is fast first and then slow, and which is slow and then fast.

Item b is incorrect: at time t3 the total time and total displacement are equal, then the average velocity wants to be equal.

Item C is incorrect: OC AB, then the slope of the line segment OC and the slope of AB are equal, i.e. the said velocity should be equal.

Item D is incorrect: at moment T3, the displacements coincide, indicating the encounter.

Item A is correct: Because A has a large velocity at the beginning and B has a small velocity. So, the distance is getting farther and farther away.

In the figure, po represents atmospheric pressure.

Figure 1 Pa = Po because point A is on the liquid surface, and its pressure is equal to the atmospheric pressure on the liquid surface.

PB is below the liquid surface, and the vertical depth from the liquid level is H1, so its pressure = the pressure generated by the liquid H1PG plus the atmospheric pressure from the liquid surface.

pb=po+h1pg。

Similarly: PC=PO+H2PG.

Figure 2 The pressure generated by the gas pressure in the glass tube (downward) is balanced with the pressure generated by the pressure at depth h below the liquid surface (upward), so p1 = p liquid. The pressure of the P solution is similar to that at point b in Figure 1. So P1=PO+HPG.

Fig. 3, the pressure generated by the gas pressure in the glass tube (downward) plus the pressure generated by the liquid pressure above the liquid level h in the tank in the glass tube (downward) and the pressure generated by the pressure at the liquid level (upward) are balanced, so that P1+HPG=P liquid level, which is the same as point A in Figure 1. p1+hpg=po，p1=po+hpg。

Fig. 4 shows that there is a small circular surface in the middle of the bottom of the U-shaped tube, and the liquid in the tube is stationary, indicating that the pressure on the left and right sides of the small circular surface is balanced, that is, f left = f right. f = ps, p left s = p right s, s are equal, so p left = p right, and p left = p1 + h pg, p right = (h down + h) pg + po, p1 + h p g = (h down + h) pg + po

p1=hpg+po。

Figure 5 is similar to Figure 4, except that the pressure p right on the right = (h down-h) pg+po.

So P1=PO+HPG.

Select b - because the direction of the current is along the lightning rod upwards, and the direction of the magnetic field is south to north, apply the left-hand rule - know the direction of the magnetic field force of this current: west!

According to the left-hand rule, the answer is due west.