Thank you for the following detailed explanation of high school physics

The first question, maybe the title is not clear, the elevator starts with a speed of 3m s, does an acceleration movement, and then obtains the acceleration through the egg yolk dynamometer should be 2m s (2), after 1s, with the formula s=1 2at(2)+v(0)t, get, s=4m

The second question, hey, this kind of question is the most troublesome, which is equivalent to two questions! The key to solving the problem is the angle between and . If you make a mistake in the diagram on your paper, you will find that there are only 3 forces that make up the equilibrium force system, namely t1 (in the direction along ), t2 (in the direction along ), and f (the gravitational force of the ball itself).

In this case, because the other forces are already known, the gravitational force of the ball can be obtained according to the angle.

Then analyze the state of the ball when it is cut (it is easy to mistake that the force on is still there, but in fact, when it is removed, the inelastic force also disappears), so the ball is only subject to gravity. The answer is C

If it is sheared, then the ball is affected by the combined action of t1 and f, which is actually the opposite force of t2 (think for yourself). This is the acceleration a=t2 m, instantaneously horizontally to the left. The answer is b

Am I rubbing? Am I doing something wrong? How can there be two answers? LZ is not strange to laugh.

Solution: 1) The indication of the spring dynamometer is less than the gravity of the object, indicating that the object is in a weightless state at this time.

Acceleration a=(g-f) m=2m s 2

There are two possibilities:

1. The elevator accelerates downward.

At this time, the displacement s1 v0t+1 2*a*t 2=4m2, and the elevator moves upward.

At this time, the displacement s1 v0t 1 2*a*t 2=2m2) suddenly cuts the thin wire ii, and the combined external force is to the left, and the magnitude is t2, so the acceleration a=t2 m direction is horizontally to the left.

Analysis: Assuming there is no wall, it is a periodic motion of a single pendulum; With the addition of walls, the movement cycle becomes half of what it would have been without walls. (The movement of a single pendulum is completely symmetrical about the lowest point of the left and right movements in one cycle).

Vibration period: t= (l g).

Periodic image: cosine.

Dear, this is a math problem I can't see the numbers clearly, you name it...

Select d to find the two rectangles on the side first, which are 2 2 2 = 4 under the root number, and then find that the surface is high, 2 the semi-circumference of the semicircle ( )2 (the garden is a radius of one), and then find the top view, 2 triangles (2 under the root number, 2 under the root number, 2 1 2) + 2 the area of the semicircle (= the area of a circle = ).

Sorted out 4 roots under the number 2+2+3

The overall analysis of the system of m1m2 objects: f1-f2=(m1+m2)aa=10 5=2m s 2

For m1 use Newton's second law f-f2=m1a

F bomb = F2 + M1A = 20 + 2 * 2 = 24N

The spring dynamometer should read 24N.

A c is wrong. b.At the moment when f2 is abruptly removed, the acceleration is changed to 12dAt the moment when F1 is suddenly withdrawn, the acceleration remains the same, for 2, are you copying the wrong question, swollen is not right.

This question is simply frustrating, none of the 4 options are right!

Since the velocity of the object is constant, it is obvious that the problem can be solved by using proportions to reduce the problem to:

The professor leaves A at 5 a.m. and arrives at B 0 a.m. early

The professor leaves A at 4 a.m. and arrives at B 20 a.m. early

The professor left A at 4:12 and arrived at B a few days earlier?

From 5 o'clock to 4 o'clock, a total of 60 parts, then we can calculate that for every minute that the professor leaves A early, he can get to B 20*(1 60) minutes (i.e., 1 3 minutes) early

Now the professor leaves A at 4:12, that is, he leaves A 48 minutes early, which means that he can get to B 48 * (1 3) minutes = 16 minutes early

Consider the whole system.

The force balance in the vertical direction of the system is fsin + support force = (m1 + m2)g

Horizontal force equilibrium Resistance = FCOS

<> look at Brother Lu. The person who sues the bird is healthy and healthy, and the family is happy!

The speed of the planet's attack is several degrees: v=2 r beats first t

By Newton's second law: gmm r 2 = mv 2 friend loss r

m about to go. to gain stellar mass.

The size of the <> may be d because the FSIN may be greater than mg3The trolley moves to the left of the bureau, and the acceleration degree is to the right, and the resultant force is to the right, only t and g are needed, then n may be 0

The trolley moves to the right, and the acceleration is also to the right, as above.

Zheng Bi In the same way, you can get c.