A high school physics problem, I hope to explain it in detail!

Analysis] is in the positive direction of vertical downwards.

During the ascent process, the velocity of the ball is vertically upward, and it is subjected to air resistance kmg, and it is also subjected to gravity mg, the resultant force is (k+1)mg, and the acceleration is (k+1)g

During the descent, the velocity of the ball is vertically downward, it is subjected to air resistance - kmg, and also by gravity mg, the net force is (1-k) mg, and the acceleration is (1-k) g

The displacement of the two processes is equal, and the acceleration of the ascending process is large, so the ascending process time is short, and a is correct; The displacement of the two processes is equal and the air resistance is equal, so the two processes do the same amount of work to overcome the air resistance, b is wrong; The ball overcomes air resistance through two processes to do work, and the velocity at the time of landing is less than v, so the absolute value of the change in kinetic energy during the ascent process is large, and c is correct; The displacement of the two processes is equal, the absolute value of the work done by gravity is equal, and the time of the rising process is short, so the average power of the work done by gravity in the ascending process is large, and d is correct.

The air resistance is determined by gravity, i.e., the air resistance is constant. The displacement is the same again. Therefore, the ascent and descent do as much work to overcome the resistance. Therefore it is bfalse.

b The acceleration of the ascending process is greater than the acceleration of the fall, so the ascending process time is short, the resistance does the same work, and the fs are the same, b is wrong, a is right, because the displacement of the two processes is the same s=1/2 of the square or s=average speed multiplied by time, it can be explained I'm really embarrassed not to play the formula I'm smiling, but I should be able to understand the first time I made a small mistake and chose c··· Changed it.

According to the definition of elastic force, the direction of elastic force is perpendicular to the contact surface, and the P-ring accepts balance, so the tensile force must be equal to the magnitude of elastic force, and the direction is opposite, so it is also perpendicular to the OA rod.

For B, the pull force F, the pull of the rope, and the downward elastic force of the OB against him, it is clear that the horizontal component of the pull of the rope balances F, so the pull of the rope is F sin

Solution: Let the displacement of A function of time be s A(t) and the displacement of B with respect to time is sB(t), then the distance between the two cars is the function of s(t) s B (t) and s A(t).

S A(T) v AT 5t

S B(T) V B T

s(t)＝－

When t 10 (s), s (t) has a maximum value of 25 (m) so that s(t) 0, and the solution is: t 0 (she) or 20 (s) Answer: After 10 s, the two cars are the farthest apart, and the distance is 25m; After 20s, the two cars met again.

Answer: When the speed of car B is reduced to 0, then drive in the same direction, and the speed of car A is greater than that of car B at the beginning of driving in the same direction until the speed of the two cars is equal, car B begins to catch up with car A, and the distance between the two cars begins to decrease.

Therefore, taking the direction of car A's speed as the positive, the two cars are farthest apart when passing t seconds, and the speed of the two cars is equal at this time, there is -v B + at=v A solves t = 30s when the two cars are farthest apart when passing 30 seconds.

In 30 seconds, sA = v, A, t=150ms, B = -v, B t+at, 2=-75m

So the maximum distance s=sA-sB=225m

When the two cars meet, it is when the displacement is equal, that is, S A = S B, so V A T = -V B T + at 2 The solution is t = 60s, and after 60 seconds, car A meets car B again after 60s.

It's actually a math problem<>

How are those two cylinders arranged?

Under the action of the vertical downward pull f, it remains stationary. At this time, the weighing pan is in equilibrium, and it is subjected to the upward pulling force f1 of the spring to him and the gravitational force g and the external force f2 that it is subjected to, and f1=g+f2, so the instantaneous removal of the external force f2, the spring will not return to its original state, so the tensile force of the spring remains unchanged, so the resultant force of f1 and g is 30N, so the pressure of the weighing pan of the object is 30n and the direction is vertically upward.

10 N because the pressure of the object on the weighing pan is unchanged due to the sudden withdrawal of pressure.

Hello, do I need to provide you with a high school physics problem?

Questions. <>

Okay, wait a minute.

Questions. The mass of the slider and the skateboard is 1 kg, and the question is the acceleration of the skateboard?

Hello, the acceleration is 6

a g sin37° g 10 sin37° question. <>

Because f = m total a

So a=f, m, total=30, 3m, s2=1, 0m, sfn-mg=ma

So fn= mg+ ma=20n

Let the speed of sound be v1, the speed of the aircraft be v2, the time from the top of the head to the discovery of the plane is t, the distance from the flight altitude of the aircraft to the top of the head is a, and the distance from the plane directly above to the visual position is b, then there is a=v1*t, b=v2*t

Because b a=tan30, i.e. v2*t v1*t=tan30. Therefore v2 v1=tan30

The ratio of the quantities of matter is 1 16:1 18:1 44 = 99:88:36

The ratio of atomic numbers is (99*5):(88*3):(44*3)=15:8:4

Ratio of volume = Ratio of quantity of matter = 99:88:36

Under the same conditions, the ratio of the mass of the three gases CH4, H2O(G) and CO2 is 1 8:1 9:1 22, and the ratio of the number of atoms contained in them is 5 8:

1 3:3 22, the ratio of the volume occupied is 1 8:1 9:

1. The ratio of the quantity of matter is how many moles of CH4, H2O, and CO2 are in the case of the same mass, assuming that the mass is one, the fraction obtained by their mass fraction is the amount of their substance.

2. After obtaining the amount of each substance, 5*N(CH4):3*N(H2O): 3*N(CO2) is the ratio of the number of atoms contained.

3. Mixed gases are the same as single gases, they are: , as long as you calculate how many moles of CH4, H2O, and CO2 each, these three empty spaces will come out The method tells you, do the math yourself The most important thing in learning science is practice