Ask the master to help solve a few physics problems in the first year of high school, and give a hig

1 Free fall v0=0, x=, from x=1 2gt, solution t= So, the first time to the ground velocity is v=gt=4m s

The second time, it can be regarded as an upward throwing motion, due to the symmetry of the upward throwing motion, known.

The second time to the ground speed is still, and the subsequent movements can be regarded as upward throwing motion.

So the velocity to the end of the ground is.

2 Free Fall v0=0 vc=v vb=3 4vac=v 2 2g ab=(3 4v) 2 2g ac-ab=7m

Substituting the solution to v 2 = 320

Substituting AC=16M

3 b brake, as a uniform deceleration linear motion Finally, the rest v0 = 0x = 1800m vb = 30m s va = 10m s is solved by vb 2 = 2ax to obtain a = -1 4

b The time from the start of braking to a standstill.

vb+v0) 2*t1=x, and the solution t1=120 lets ab meet time t

Then vb*t+1 2at = 750+10t

The first question is too vague and is divided into three processes, the first.

The first and third are free fall, and the second process is collision;

Question 2: A can be on Mars;

Question 3: Calculate the acceleration a from 1800m and the muzzle velocity, and collide when the time t is set.

How do you calculate a range? In fact, if you want to look at the upper as a solid body, the tensile force f does not necessarily go up along the bevel. The force f in the figure is also parallel to the inclined plane, so the tensile force has a range, and the object may move upwards along the inclined plane perpendicular to the boundary line of the slope top, or the direction of displacement may be at an angle to the slope top boundary

There are two scenarios for an object to move upwards.

The first tipping point. The tensile force is on the same line as the gravitational component of the object's frictional force. In the opposite direction. This f should be the smallest.

The second tipping point. The component of the tensile force is just enough to level the horizontal friction and the gravitational component. The object accelerates horizontally to the right along the inclined plane, and in this case the pulling force f is maximum, and as long as it is less than that, the object can move upward.

As we know from the title, in the direction parallel to the inclined plane, the object moves with a uniform acceleration with an initial velocity of 0.

The acceleration a can be found by dividing the square of the 3-order deformation formula s=v by a f=ma and the total force in the inclined plane direction f total = f-mg multiplied by sin37 The formula is reversed.

Rated speed n = 210 * 60 = 12600 rpm hour circumference l = d = * km.

The rated speed v=nl=12600*kmh c is correct.

Select C for an hour the wheel rotated 210 * 60 turns, the distance of each turn of the electric car is the circumference of the wheel, that is, meters, then the distance of the electric car in one hour is 210 * 60 * meters, about 20km, the rated speed of the bicycle is 20km h

The velocity in the direction along the rod is the same because the rod cannot be stretched, so the answer is v0cos30= 3 2v0

H is the height of m.

You've got the decomposition of velocity in the wrong direction.

The velocity of m moving to b is the partial velocity of the velocity of a in the direction of the rod, so the straight line where the rod is located should be made as a perpendicular line to obtain v='

Instead of passing v. Make perpendiculars.

This problem can't be calculated in this way, this should be the same as a person pulling a boat, with a circumferential pendulum, the movement is a and velocity, you have to break it down into a circular motion perpendicular to the rod, and then calculate... Know how to get up three.

The content of the 22 questions of the 09 Anhui Science and Technology Comprehensive: (text omitted).

It is known that the athlete has a mass of 65 kg and the lift has a mass of 15 kg, and the athlete is rising with the lift at a 1 m s2.

Find: (1) the force of the athlete pulling the rope vertically downward;

2) Athlete's pressure on the chairlift. (Excluding the friction between the pulley and the rope, g 10m s 2).

Solution: (1) If the force of the athlete pulling the rope vertically downward is f, then the whole composed of people and the chairlift has 2*f (m m)*g (m m)*a

2*f－（65＋15）*10＝（65＋15）*1

The required pulling force is f 440 N.

2) Analyze the force on the chairlift: gravity mg, the pulling force of the left rope f, and the downward pressure of the athlete on it n

From ox two, f mg n m*a is obtained

440－15*10－n＝15*1

The required pressure is n 275 N.

1. All can be known from the title.

a=-2m/s^2

So x5=15*5-1 2*2*5 2=50m, and the velocity is zero after x seconds, x=v a=

Because it is less than 10s

Therefore, the braking distance between the car and the braking distance at 10s is the braking distance of the hour, so x=

The initial velocity v0=15m s, and the acceleration a=m s 2;

The time required to reduce the velocity to 0 is t1=v0 a=15 2=;

That is, the car comes to a complete stop at the first brake, so "How far is the car from the braking point at the end of 10 seconds after braking?" ”

Only use to calculate the distance between the beginning of the brakes and the first rear.

That is: s2=v0*

How far is the car from the start of braking at the end of 5 seconds after braking:

s1=v0*

v0t+1/2at^2

Note that a is a negative number, and the distance is 50m

The same goes for the above, but the car has already stopped after 10s, and it should have stopped in seconds, at this time, the reverse solution is directly 1 2at 2=s.

s=vt+at2, where v=15, a=-2, t = 5 and 10 respectively, just set the formula to find s.

Oh, 10 times it's not a formula.

To use vt=vo+at, use it to find out how much time it took for the car to stop, and then use that time to set the top formula to figure it out here vt=0,a=-2,vo=15

It's easy, but I don't either.

Considering that in 1s, w=p*1s, q is the flow rate (q*v 2) 2=p, and the horizontal range is 1:2, then the initial velocity is 1:2, so q1:

q2=4：1，v1:v2=1:

2,t1:t2=1;8

The power is the same, that is, the water flow per unit time is the same ((the distance is because the cross-sectional area is small and the flow rate is fast).

If the depth is the same and the base area is 1:2, the volume is 1:2

Then the time is naturally 1:2.

Now that you understand the answer, it's easy :

In order to illustrate the two answers to cd, let's prove b first:

Quantity q=it=(magnetic flux) r, so b is correct.

Since Q1 = Q2 (Q1 and Q2 are used to represent the amount of electricity from A to B and B to C respectively), i(1)t(1) = i(2) t(2) i.e., (1 in parentheses, 2 is the subscript) bi(1) lt(1) = bi(2) lt(2) i.e., the impulse of the ampere force in the two processes is equal.

Since the impulses are equal, the change in momentum is equal, i.e., the change in velocity is equal because the velocity at c is zero, if the velocity at b is v, then the velocity at a is 2v According to the kinetic energy theorem, it can be obtained that c is correct d is false, and d should be equal.

Science students passing by... I really don't want to count ==

It seems that it can be calculated by the microelement method, that is, by integral.