When the acceleration is O, is there still a direction When the velocity is O, is there still a dire

When the acceleration is 0, there is no direction if it is at rest, and if it is moving in a straight line with uniform velocity, the velocity has a direction, but the acceleration has no direction. This is easy to understand, so I don't need to give an example.

When the speed is 0, there is no direction. It can be understood in this way: the direction is a trend, which is a quantity defined by the position of the moment and the next moment, divide the difference between the position of the next moment and the position of the moment by time, and then find the limit t->0, and the result is that the direction is zero in several coordinates, so the direction is also zero when the velocity is zero.

For example, in the vertical upward throwing motion, when the particle is at the highest point, the velocity is 0, and the acceleration is not 0, and there is no direction at this time.

Acceleration or velocity, as a vector, direction is defined as the direction of the vector line segment, or the angle between the vector line segment and a certain axis (generally the x-axis), the zero vector is a point, it does not point, and it cannot form an angle, of course, there is no direction, acceleration and velocity are mixed together It is easy to mislead you, mistakenly take the direction of velocity as the direction of acceleration, or the direction of acceleration as the direction of velocity, you imagine a stationary object on the ground, the resultant force is zero, so does the resultant force have a direction? Of course not, the same reasoning. This holds true for all vectors.

When the acceleration is 0, the velocity may or may not have a direction For example, the velocity of a uniform linear motion has a direction, but the acceleration has no direction.

When the velocity is 0, the velocity has no direction, but the acceleration may or may not have a direction, for example, the velocity decelerates from 10m s until --10m s, and the acceleration has a direction.

When an object remains at rest, acceleration and velocity have no direction.

Velocity and acceleration are vector quantities, and as long as vectors exist, there must be a direction. But 0 means that there is no vector, since there is no vector, how can the direction of the vector come from.

Acceleration of 0 is no direction and velocity of 0 is possible direction.

Remember the definition of a 0 vector? The size is 0 and the direction is arbitrary, so they are all directional...

Your "direction" here is a bit vague, and speed and acceleration can discuss the direction problem.

When the acceleration is 0, there is no direction problem with the acceleration because it has no meaning, and the velocity should also be discussed on a case-by-case basis, if the object is stationary before the acceleration is 0, then the velocity is also directionless, and before the acceleration is 0, the object is in motion, then the object will move in a straight line at a uniform speed.

When the speed is 0, it is meaningless to discuss the direction of the velocity, and the acceleration may not be zero at this time, then if the moment the velocity is 0, there is acceleration, then the acceleration has a direction, for example, the car slowly decelerates from reversing until the speed decreases to 0 and then continues to accelerate forward, then at the moment when the speed of the car is 0, the acceleration is large and small, and there is also a direction.

Uniform linear motion.

When an object has an initial velocity of 10m s and an acceleration of -10m s, its velocity is 0 after 1 s, but it has a direction and a short time. Vertical upward throwing motion.

The acceleration should be changed to "centripetal acceleration", otherwise, it may be a tangential circle acceleration, and the tangential acceleration is parallel to the direction of velocity, not perpendicular.

The acceleration of the motion of a circular motion of a mass is formed by the addition of centripetal acceleration and tangential acceleration.

If the direction of acceleration is forward, it means that the tangential acceleration is in front, that is, the tangential velocity of the particle is increasing, that is, the rotation is faster.

It's an accelerated motion, but not necessarily a uniform acceleration motion. The initial velocity is greater than zero, which means that the direction of the initial velocity is the same as the positive direction chosen, and the acceleration is greater than zero, which means that the direction of acceleration is the same as the positive direction chosen, so that the direction of the initial velocity is the same as the direction of acceleration, and when the direction of acceleration is the same as the direction of the initial velocity, the particle moves with acceleration.

If the acceleration remains constant, then the particle will move uniformly at acceleration, that is to say, to move at a uniform acceleration, the condition of constant acceleration must also be satisfied.

<> if v is greater than 0, a is greater than 0, and a is unchanged, the direct drawing (v-t diagram) or the relationship between v and t can be obtained, and it can be concluded that it is a uniform acceleration motion.

Initial velocity and acceleration are in the same direction, but it is not necessarily a uniform acceleration because acceleration may change all the time.

The first thing to do is to clarify the concepts of scalars and vectors. Scalars can be compared to size, vectors cannot be compared to size, and the size of vectors can be compared to size.

Therefore, it is inappropriate to directly say that the initial velocity is greater than zero and the acceleration is greater than zero.

Since the direction of initial velocity and acceleration are not stated, the direction of initial velocity and the direction of acceleration can be arbitrarily angled.

Unless the magnitude and direction of acceleration are constant, and the value of acceleration is greater than 0, it is a uniform acceleration motion. In any case, whether it is a uniform acceleration motion or not has nothing to do with the initial velocity.

If this is a discussion of linear motion, then the latter conclusion can be drawn.

According to Newton's second God's law, the direction of the resultant force of the object determines the direction of the speed of the circle.

So the direction of acceleration is the same as the direction of the resultant force

So the answer is: resultant force.

Whether the speed increases, the key is to see whether the acceleration is in the same direction or the opposite direction as the velocity of the object, accelerating in the same direction and decelerating in the opposite direction. It has nothing to do with the direction of displacement, this statement is, of course, wrong.

For example, if the train enters the station to decelerate, and the station is the zero point, then the displacement is getting smaller and smaller, but the displacement is pointing from the station to the train, and the displacement is in the same direction as the acceleration, but the speed is getting smaller and smaller.

The main reason for this problem is that the starting point of the displacement can be set freely.

In a rectilinear motion, if the direction of acceleration (a) is the same as that of velocity (v), and the acceleration gradually decreases to zero, the change in velocity will depend on the initial velocity (v0) and the rolling velocity (vf).

When the acceleration is in the same direction as the velocity, i.e., a>0, the velocity gradually increases until it reaches a maximum (vf) and then decreases until the acceleration becomes zero. In this case, the initial velocity (v0) of the acceleration is less than the final velocity (vf).

When the acceleration is reversed to the velocity, i.e., a<0, the velocity decreases until it reaches a minimum (vf) and then increases until the acceleration becomes zero. At this point, the initial velocity (v0) of the acceleration is greater than the final velocity (vf).

To sum up, the initial velocity of acceleration is the velocity at which the velocity begins to change, and the end velocity is the velocity when the acceleration becomes zero.

Acceleration characterizes the speed of the change in velocity, acceleration = (end velocity - initial velocity) interval time; Therefore, as long as the acceleration is greater than zero, that is, the direction of acceleration is the same as the direction of velocity, it means that the final velocity is greater than the initial velocity, that is, the velocity must increase.

When the acceleration is zero, that is, the direction of acceleration is opposite to the direction of velocity, indicating the end velocity and the initial velocity, the velocity decreases, and the object decelerates in motion.

Added: The acceleration remains the same, it is a linear motion with uniform variable speed! The acceleration of a uniform linear motion a=0!

Answer: The direction of acceleration is opposite to the direction of velocity, and when acceleration is reduced to 0, the velocity may or may not be 0

The direction of acceleration is opposite to the direction of velocity, the object decelerates, the acceleration decreases, the velocity decreases slowly, and when the acceleration decreases to 0, the velocity of the object may decrease to 0; It may also be reduced to a certain value and then move in a straight line at a uniform speed.

The speed doesn't have to be zero, it's just that it doesn't change anymore.