Interesting Physics Problem Solving!! By speed and rate Pick the answer merit based

The moment the clouds collide, lightning and thunder are generated, assuming that the flash of light reaches the human eye after the time of the t-ray;

Then the thunder passes through (t light + time to reach the human eye.

The distance does not change to s

It can be concluded that:

s = v light * t light.

s = v sound (t light +

Thus it is obtained: v light * t light = v sound (t light + t light to the -5th power.

s = v light * t light = 3 * 10 8 times * -5 power meter = km. a

Choose B, it should be meters, but 340 1000 1 3, so the distance is about.

The answer should be b and d. Because the speed of light is much larger than the speed of sound, it is physically called much greater, so the speed of light does not have to be considered.

It seems that I just told my little brother about this question, and it would be good to do more of this type of question, and the answer means that the speed of light is too fast, so the time of light is omitted, and the speed of sound can be calculated directly, and it seems that B is selected. I still have that book at home, and the answer is that it's written that way, and D is correct. The first person's algorithm is correct, but the difference between the result and the rough result is only 82 meters, and the problem is finally counted in kilometers, so it can generally be omitted for high school physics.

a When lightning occurs, thunder is broadcast at the same time, and the distance traveled by lightning and thunder is the same.

3*10 to the eighth power m s multiplied by x seconds = (x + seconds multiplied by 340 ms solution to get x = seconds.)

So the distance is x times 3*10 to the eighth power =

Since the speed of light is much greater than the speed of sound, the time of light is negligible.

The velocity of the sound in the air is between, then the distance sought x=vt= is approximately equal to t 3 because the time t=

So the distance x=

The answer is a. It should be estimated that the speed of light is too fast to be negligible. It should be directly with the speed of sound 340 seconds 4182 meters.

Xiao Wang's estimation is a coincidence here, and the estimation method is not advisable.

b I'm not from Zhejiang, but I've seen this question, first of all, the speed of sound is very different from the speed of light, so the speed of sound is ignored, and the answer is b

Option B In this case, the speed of sound is much smaller than the speed of light, and the time difference can be ignored. Is that right?

In both cases, when the velocity is smaller, the ball will hit the wall of the pit near side A, and when the speed is high, it will hit the wall of the pit near side B.

Let the radius of the circle be r

When the speed is smaller:

The time it takes for the ball to hit the pit wall is t1

Then t1 = root number (r g).

At the same time, there is v0t1=1 2(2-root number 3)r

Substitute formula 1 into formula 2, and transfer the term to the general division.

r=v0 [2 (2-root number 3)] g can be obtained in the same way, and case 2 can be obtained.

r=v0 [2 (2 + root number 3)] g

The ball suspended on the roof of the trolley deviates from the vertical direction angle, and the ball deviates to the left, then the motion of the trolley may be:

a Accelerated movement to the right.

and dDecelerate movement to the left.

Because, due to the acceleration of the car to the right, and due to inertia, the ball still has to maintain the original motion state, and the phenomenon of left deviation is generated; Due to the deceleration of the car to the left, and due to inertia, the ball still has to maintain its original motion state, resulting in the phenomenon of left deviation.

According to inertia, there are two possibilities for the ball to deviate to the left, one is to accelerate to the right, and the other is to slow down to the left. Therefore, AD is chosen.

Inertia issues.

The ball deviates to the left indicates that it receives a force to the right, so the motion of the car may be an acceleration motion to the right or a deceleration motion to the left.

If the ball deviates to the left, it means that the resultant force is to the left, so choose BC

b Deceleration movement to the right c Acceleration movement to the left.

Because there is friction and relative motion! Calculate the distance of their relative motion and compare the length of the conveyor belt....Take a small straight ......

Ask first. The static friction of an object (the critical value at which the object slides up) can be understood as the tensile force experienced by the five pieces on the belt.

Further find the acceleration of the object.

Well after accelerating to 6m due to the belt.

Know. Exercise time.

The one that slows down.

Just repeat 1 mile and can be removed.

But the time is 2 seconds).

Finally, s = solve.

Known: Standard = 3rd power (kg m3).

V saline = 500 ml = -3 power.

m Saline = Seek: Saline.

Solution: The density of the brine is .

Saline = m brine v brine = 3rd power (kg m 3) saline standard.

Therefore, the salt water prepared does not meet the needs and water should be added.

1.Solution: (1) Because the gravity of the B ball is balanced with the tensile force of the rope after the B ball turns 90°, the force of the B ball is zero, and p=0 is obtained according to p=fv.

2) The question says: "When the pressure of ball A on the ground is just zero", so (speechless).

2.You add the diagram, and I'll help you make the diagram even more speechless

1.The instantaneous power is p=fv, v is the velocity along the direction of the force, and the velocity of b is horizontal and zero in the vertical direction, i.e., in the direction of gravity, so p=0A has already said in the question that the ground pressure is zero.

2.What about the second question?

1.The work done is the displacement in the same direction of the force, and the form of the marble is not given here, so it should be the size of the disregard.

Raise it to the upper surface to be level with the water, and the buoyancy force experienced in the process does not change, and therefore the pulling force does not change.

Namely, W FS 544x2 1088J

I'm sorry.,Time relationship.,I can only do one question.。。 I hope it can help you.

Solution: The electric field force in the horizontal direction f=2*2=4n, and the acceleration in the horizontal direction a1=40 3

The vertical direction is subject to gravity g= and the acceleration in the vertical direction is a2=10

Let the time it take for the particle to reach the point directly below point o for the first time t

Then 1 2*a1*t 2=6 gives t 2=9 10

So the height of the descent h= 1 2*a2*t 2 = 1 2*10*9 10 =

1) From the kinetic energy theorem, we get eql+mgh=1 2*m*v1 2

So the increment of mechanical energy e=1 2*m*v1 2 — mgh =eql+mgh — mgh =eql=4*6=24j

2) From the kinetic energy theorem, eql+mgh=1 2*m*v1 2 i.e., , and the arithmetic square root of v1 2=250 i.e., v1=250 is obtained.

The electric field force in the horizontal direction f=qe=

The horizontal force of gravity is greater, so the rope has not been straightened when the particle is directly below o, the horizontal initial velocity is 0 in a uniform acceleration motion, and the vertical direction is also a uniform acceleration motion with an initial velocity of 0.

s=v0t+at……2/2

Horizontally: 6=(4, push-out, t2=9, 10

Vertical direction s=10*t 2 2 pushout s=m) (1) The increased mechanical energy does the work for the electric field force: w=fs=4*6=24 (joules) (2)w1+w2=4*6+3* pushout v1=5 (root number 10).