14 questions, 2 Physics Compulsory in Senior 1, 2 Compulsory 2 in Senior High School, 4 question on

When the rope is disconnected, the speed of the ball and the elevator is v, and after the time t the ball meets the elevator floor (that is, the ball falls on the bottom plate), take the vertical upward direction as the positive direction, then:

The displacement of the elevator floor is x=vt+1 2*at 2, and the displacement of the ball is x'=vt-1 2*gt; 2, when the ball meets the elevator floor, the displacement of the floor is more h, x-x'=h, so t=.

If it is in the elevator movement'=1s after disconnection, at this time the velocity of the ball and the elevator is v=at'=10m s, in the time when the ball falls on the bottom plate, from the person on the ground, the ball is decelerated and rising, its acceleration is downward, the size is g=10m s 2, its muzzle velocity is upward, the size is v=10m s, (the time for the ball to rise is t.)"=v/g=1s）

Within the time when the ball falls to the base plate t=, the displacement x'=vt-1/2*gt^2=。

1) According to h=1 2(at), we get t=under the root number (2h (g+a)) (please ask if you don't understand).

2) Downward acceleration movement, acceleration 20m s

Displacement x=1 2(at)= (This one is a bit uncertain.) Copy the translation results to Google Translate.

Therefore, as long as the height of the water column h is measured, the buried jet velocity can be estimated v0, and the height of the fountain water column can be compared with the height of our people or the known height of a building, so as to make an estimate.

The expression v0 obtained from v2=2gh is: v0=root number 2gh

Answer: Song Zi socks are like wild hail pictures:

1000 r (in rad min) = . Pi.

If yes, I'll tell you how to solve the problem.

That's a good question! I'm still a high school student!

Let me remind you, the speed r*s (the circumference of the wheel) = speed v and pay attention to the conversion of units! The rotational speed, circumference, and length in velocity are all reduced to meters m, and time is reduced to seconds.

It's not that I'm dampening your enthusiasm, hey, I'll tell you, the current students are not easy to be, and they are very competitive!

Solution: The radius of the car is r=30cm=

Then the circumference of the sedan is l=2 r=

When the speed is 120*10 h, the number of revolutions of the car in 1h is =120*10

120km/h=120m/

So the number of turns the car has made in 1s is 120 so the number of turns the car has made in 1min is = 1

Kindness. 120km h=, and then the wheel can go 2*pi (pi) *r= by one revolution, so that you can calculate how many revolutions you need to make in a second to reach that speed. Then, the radian traveled by each revolution is 2pi (pi), as long as .

The results may be a bit different because my intermediate steps keep two decimal places, and it's best to always use a calculator to figure it out, and keep at least 6 digits for the intermediate steps, so the result should be fine.

Solution: The circumference of the wheel l=2 r=(2

The car turns in one hour r=(120000

The speed of the car at this time n=r t=63694r 3600s=

Rice. Rice.

In the first question, the velocity of the object when it reaches the conveyor belt is greater than 3 meters per second, that is, the speed of the object when it returns from the conveyor belt is 3 meters per second, and then the object can be calculated by using the conservation of mechanical energy.

In the second question, the velocity of the object is 2 meters per second when it reaches the conveyor belt, and the velocity is still 2 meters per second when the object returns, which is calculated by the conservation of mechanical energy.

If you don't understand, just ask, it's best to add some gold coins, and then you can ask me directly if you don't understand.

Although the problem is incomplete, it is still A, and the object should move in a straight line at a uniform speed when verifying the law of mechanical energy with paper tape, but the acceleration should be less than g, and the problem is so large that it is impossible, but B is even more impossible, because B is not a uniform speed motion at all, so if you have to choose, choose A

I think S1, S2, and S3 should be the distances of AB, AC, AD, so that B is closer to reality.

b, the same amount of displacement change in the same time!

It has nothing to do with the g-value, and it doesn't say the time.

This should be a compulsory question in the first question.

It should be a, and the object should move in a straight line at a uniform variable speed when verifying the law of mechanical energy with paper tape, so as to measure the velocity of the object and then calculate the change in the kinetic energy and gravitational potential energy of the object, so S3-S2 and S2-S1 are close to the square of g t, so choose A

Within 2-10 seconds. p*8-f*s=1 2mv2 2-1 2mv1 2, v1 is the velocity at 2s, v2 is the velocity at constant velocity.

where f is unchanged and is equal to the traction force at a constant velocity, so f=p v2 brings in the kinetic energy theorem to find s.

If you use the integral, you get the result according to Niu Er: p v-f=mdv dt i.e. (p v-f)dt=mdv integral: p-fv)dt=m vdv:

pt-fs=1 2mv2 2-1 2mv1 2 This is the kinetic energy theorem above.

by h=1 2gt2

T = root number 2h g = fifth of the root number five.

And vot = h tan30'= root number three.

Then vo = root number fifteen.

Time can be considered from two aspects: the component of horizontal uniform linear motion and the component of vertical free fall, since the former introduces the unknown quantity vo, so the latter is used to find time t

1 2·g·t 2=h , h=1m, find t= (1 5)s (1 5 s under the root number).

Now introduce t to the horizontal component:

vo·t=h tan, substituting t, h, , and obtains: vo= 15 m s (root number 15 m s).

h=(gt^2)/2

The bottom can be solved using trigonometric functions.

l=vtt can be found either v or wt.

The minimum radius is: r=360 (6g)=360 60=10m

The included angle is 90°