During the exam, SOS, physics, thanks

Child! That's not right! This is a pit for yourself, and the unsatisfactory test results indicate that you don't know enough about the knowledge of this place. In that case, I won't be the same next time as I am today!

Quite simply, 1) In order to keep the time as short as possible and have only one bullet hole, so that the rotation period of the paper tube is t, then the time for the bullet to travel through the paper tube is ( From the inscription, calculate t=2 w=

The velocity of the two gears is calculated separately by the formula v=s t.

v1=d/v2=100m/s

2) The question is a bit troublesome, just calculate it separately.

The magnitude of friction between CDs is fcd= fca=

So when c is faster than d, the deceleration of c is ac = 1n 1kg = 1m s ad = 1n 3kg

First of all, in the case of v1 = 300m s.

According to the kinetic energy theorem, m, the bullet v1 = m combined*v combined, v combined, v combined, = 3m s, if the final common velocity of the adc.

The velocity is v final1=300*

According to the functional formula fs=1 2 *m*v final - initial kinetic energy (writing 1 2 mv 0 etc is also OK) gives s=

The verification can also be used to find the distance according to formulas such as velocity).

It can be seen that the s > so it is not on topic.

In the case of v2 = 100 m s.

v = 1m s If the ADC has the last attack speed, then v final=fs=1 2 m v gets s=<

So it meets the requirements of the question.

After that, the flat toss begins.

vfinal=

h=5mh=1/2 gt²

t=1s is obtained

s-level = v final *t = 1*

A: The required centripetal force equation is: f=mv (r+h) B:

The equation for the strength of the gravitational field in the satellite region is: e=gm (r+h) c: from the above equation:

gmm (r+h) = mv (r+h), which can be solved:

v = gm (r+h) under the root number, obviously the greater the height h, the smaller the velocity v.

D: When the speed of the satellite decreases, the gravitational force is greater than the required centripetal force, and the satellite will gradually circle towards the earth's surface.

1.Force analysis (one weight, two bombs, three frictions draw the force).

2.Column equation to find acceleration.

ma ＝ mgsin30°

a＝g/23.The distance acceleration is calculated, and then the time is found.

Distance 1 2at

4.Find the speed.

Acceleration multiplied by time.

Sliding on a smooth slope with zero friction and conservation of mechanical energy.

mgh＝mv²/2

h＝lsin30°

Where, the sliding distance l

Solution: v (gl).

Acceleration along the inclined plane a=

From the formula for uniform acceleration : v 2= --v= (

1.Find the velocity at object b with conservation of momentum, 2The coefficient of friction is found using the equation of motion.

Conservation of first momentum, columnar.

m·v0 = m·v1 + mb·v2 substitute mb = 2ma, v0 = 4, v1 = 1, and v2 = m s, which is the initial velocity of the motion of object b.

After the object B is at rest after motion, the energy is conserved, and the kinetic energy is converted into mechanical energy, column.

1 2) MB·V2 =FL = MB·G·L substitute V2 = , G = 10, L = to get the solution

1 question timbre. 2 questions.

Since it is a glass and a hail, it is balanced.

Then another force should be applied to the glass.

The answer is the friction of the meter against the glass.

3 questions. Due to refraction.

So the bubbles of the circle become elliptical trapped circles.

Because of the reflection, there is less light in the bubble than in other places.

Shadows are formed.

Shadows are also formed through other parts.

4. The velocity of the object is meters and seconds.

The velocity of the elephant is meters and seconds (this is not certain).

5 questions. It is manifested through the deformation of the object.

6 questions. I don't know.

I didn't learn biology well.