In physics, the problem of uniform variable speed, on average, the movement of physical variable spe

You can understand it this way, car 1 relative to car 2 with velocity v1-v2, acceleration a motion, car 2 stationary, so when car 1 decelerates to 0, its displacement is less than s, car 1 will definitely not collide with car 2, by the formula v2 2-v1 2=2as, where v2=0, v1=v1-v2, due to deceleration motion, then substitute the formula as long as there is (v1 2-v2 2) 2a(v1-v2) 2 2s

The condition is that the two cars do not collide when the train speed v is equal to v2, i.e.

v1-at=v2, and s+v2t v1t-1 2at 2 is substituted by v1-at=v2 to t=(v1-v2) a to s+v2t v1t-1 2at 2 to get:

s+v2*[（v1-v2)/a]＞v1*[（v1-v2)/a]-1/2a[（v1-v2)/a]^2

s＞v1*[（v1-v2)/a]-1/2a[（v1-v2)/a]^2-v2*[（v1-v2)/a]=(v1-v2)^2/a-1/2(v1-v2)^2/a=1/2(v1-v2)^2/a

i.e. s 1 2 (v1-v2) 2 a

a＞(v1-v2)^2/(2s)

Just put the formula: v2 v1 at

Transform to: t=v1-v2 a

Substituting the formula: v1t-at 2 2(v1-v2) 2 2s

According to the formula you listed, you can solve the answer, and you are doing the math.

Bringing the second formula into the first formula gives s>at 2 2

Again, t=(v1-v2) a can be brought in.

Your only formula is wrong...

v1t is individual! Divide!

The key to this topic is that the distance traveled by the two cars after the train is evenly decelerated cannot be greater than S. Just be nice according to this column inequality

Note: Acceleration, displacement are directional

Uniform acceleration means that the acceleration a in the acceleration motion remains unchanged, that is, the acceleration remains unchanged and the velocity changes uniformly.

Uniform speed change means that the acceleration a in the acceleration motion is also changing uniformly, that is, the acceleration changes uniformly, and the change in velocity is not uniform.

Variable acceleration is an uneven change in acceleration a, that is, an uneven change in acceleration, a change in velocity, and of course even more uneven.

Summary. Cannot physical variable speed motion be regarded as a uniform variable speed on average The answer is as follows: Hello Variable speed motion is the acceleration that changes all the time.

This average is not good to measure by average. And the uniform speed refers to the acceleration that has always been the same. You can't do it.

Cannot physical variable speed motion be regarded as a uniform variable speed on average The answer is as follows: Hello Variable speed motion is the acceleration that changes all the time. This average is not good to measure by average.

And the uniform speed refers to the acceleration that has always been the same. You can't do it.

Extension: Uniform speed motion is the movement of the velocity vector with a uniform change of time, that is, the velocity change per unit time is the same, that is, including the equal size, and the same direction is required. According to the definition of acceleration:

a=δv δt, the velocity changes by the same amount per unit time, i.e., the motion with constant acceleration. According to Newton's second law, f=ma, the resultant external force of the object is a constant force. From a dynamic point of view, the motion of an object subjected to a constant force is a uniform velocity motion.

In terms of motion form, it includes uniform speed linear motion and uniform variable speed curve motion.

x=at2 means that the difference between the displacements in the Moritaka interval remains constant for a continuous equal period of time, and is equal to at.

The derivation is as follows: <>

The formula derived from the definition of uniform velocity is acceleration: a=(v-v0) t and instantaneous velocity: v=v0+at.

Displacement formula: x=vt+ at, average velocity v=x t=(v0+v) 2. (The units are all SI units, i.e. the unit of a is the attitude m s, the unit of x is m, and the unit of v is m s).

s1=at^2/2

Take the direction you started to go in the positive direction.

s2=a1t*t-a2t^2/2

Yes. s1+s2=0

That is, 3*a1t 2-a2t 2 2=0

Simplify to get a1:a2=1:3

First question:

Passing in the first second, apparently by s=1 2*at2, substituting s1= and t1=1s, the acceleration a= can be obtained.

Then by the formula s=1 2*at2, the acceleration a, the distance s=12m, substituted in, and the result t=4s can be obtained;

Second question:

By v=at, substitute a=, t=4s into the formula, you can get v=6m s Note, if the above formula is not clear, go to the book.

1.Because people do a uniform linear motion with an initial velocity of 0.

s=1/2at2

Solution: a=s total = 1 2at2

t=4s2.Because vt=v0+at

So vt=0+

Method 1: The displacement of the car from this second is 4m', which means that the velocity at the end of the 3s is 4ms

Acceleration a=(v2-v1) t=(4-6) (3-2)=-2m s 2

The initial velocity v0=v1-at=6+2*2=10m s

Because the deceleration time t0=v0 a=10 2=5s, the displacement within 6s after braking is s=(v 2)*t0=25m

Method 2: The car moves in a straight line with uniform deceleration.

The displacement of the car from this 1s is s1 = 4m

The time interval from to t1=

3S end velocity vt1=s1 t1=4 1m s=4m s

The time interval from the end of 2s to the end of 3s t2=3-2s=1s

The acceleration of the car a=(vt1-vt) t2=(4-6) 1m s 2=-2m s 2

The muzzle velocity of the car v0=vt-at=6-(-2) 2m s=10m s

The time from braking to stationary of the car t=(vt2-v0) a=(0-10) (2)s=5s

That is, the car has stopped for 5s after braking.

The displacement within 6 seconds after the brake of the car is the displacement within 5 seconds after the brake of the car.

The displacement of the car within 6s after braking is s=v0t+1 2at=10 5+1 2 (-2) 5 2m=25m

Analysis: The change of velocity (or magnitude or direction) (i.e., a≠0) is called variable speed motion;

Uniform speed motion may be either linear motion (uniform variable speed linear motion) or curved motion (e.g., flat throwing motion);

The motion through the same displacement at any time is called uniform motion.

Constant motion refers to motion with constant velocity and 0 acceleration.

Uniform velocity motion refers to motion with constant acceleration.

Variable speed motion refers to the movement in which the acceleration is not 0 and the velocity changes.

The relationship between them is that uniform motion is a true subset of uniform velocity motion, and uniform velocity motion is a true subset of variable velocity motion.

Constant motion: The same distance is traveled per unit of time. The magnitude direction of the velocity remains the same.

Variable Speed Movement: A movement in which the magnitude of the speed is constantly changing. It is divided into uniform speed movement and non-uniform speed movement.

Uniform speed movement: The change in velocity per unit of time is the same. It can be divided into uniform acceleration and uniform deceleration.

First of all, it should be explained that "uniform velocity" means that the acceleration is constant (the magnitude and direction are constant).

Uniform acceleration motion means that the combined external force is a constant force, and the angle between it and the direction of velocity is an acute angle (such as flat throwing motion, free fall motion).

Uniform deceleration motion means that the combined external force is a constant force, and the angle between it and the direction of velocity is an obtuse angle (such as the movement of an object thrown upwards in the ascending stage, excluding air resistance).

Note: 1. Because it is not stated that it is a linear motion, the above content includes linear motion and curved motion.

2. If it is a linear motion, the combined external force and velocity in the above content are in the same straight line; If it is a curvilinear motion, then the resultant external force and velocity are not in the same straight line.

The direction of acceleration is consistent with the initial velocity, which is acceleration, and deceleration is inconsistent.

Just look at the former, and the other upstairs is wrong, the direction of acceleration is the same as the direction of initial velocity, acceleration motion, on the contrary, deceleration, other angles will cause the object to change the direction of motion and do curvilinear motion.

Latter. Or, faster and faster is adding.

Otherwise, it is minus.

Accelerated motion, the direction of acceleration is consistent with the direction of the object's velocity; Uniform acceleration motion refers to the acceleration motion with the same acceleration value; Uniform deceleration motion: refers to the acceleration in the opposite direction to the direction of motion of the object.

To be precise, the direction of the resultant force (acceleration) and the velocity is less than 90 degrees, otherwise it is deceleration, and when it is 90 degrees, it moves in a circle, but the two words uniform velocity refer to the magnitude and direction of acceleration have not changed.