In order to study the situation of doing curvilinear motion in a plane

The actual motion of an object can be seen as the combined motion, and we can decompose this actual motion, that is, the combined motion. The relationship between the split and the combined motion in the two directions after decomposition follows the parallelogram rule.

A false. The relationship between the displacement of the combined motion and the displacement of the sub-motion is the relationship between the composite vector and the sub-vector --- follows the parallelogram. It is not possible to add or subtract directly by algebraic methods.

b correctly according to the parallelogram rule, the two sub-displacements are the two sides of the parallelogram, the diagonal of the combined motion. A parallelogram is two triangles, so the bevel is the combined displacement, and the two right-angled sides are the partial displacement.

C false. Velocity is also a vector quantity and again follows the parallelogram rule. It cannot be summed algebraically.

D false. Following the above decomposition of the two mutually perpendicular directions, the combined motion is a diagonal of a rectangle and cannot be smaller than a right-angled side.

a is the sum of vectors rather than algebra and vectors (e.g., displacement velocity) are added to vectors and scalars (e.g., temperature) are added to algebraic sums.

b correct. c is a vector sum rather than an algebraic sum.

d is indeed possible, but only if the two partial velocities are obtuse. This is not possible with the partial velocity of the flat tossing motion on the two axes of xy.

In a vector triangle composed of displacement and velocity, the two components of the x-y axis are both squares equal to the squares of the hypotenuse. and not simply algebraic sum.

Normally, curvilinear motion is studied in a two-dimensional plane, because curvilinear motion involves the state of motion of an object on a plane and various factors.

On a plane, the trajectory of a curvilinear motion can be described by the position of a moving object in a coordinate system as a function of time. According to the change of position with time, the physical quantities of the velocity and acceleration of the object can be deduced.

However, in some special cases, curvilinear motion may also involve three-dimensional space, such as objects flying in the air or particles moving at high speeds. In this case, a three-dimensional coordinate system is needed to describe the position of the object's motion over time.

In summary, curvilinear motion can be studied on a flat surface or in three-dimensional space, depending on the motion of the object being studied.

The answer to this question: a.

Analysis: Because there is a change in the direction of the velocity of the curve, there must be acceleration, so a is correct.

The motion of the projectile (including the flat and oblique throw) is the curvilinear motion of the acceleration without the same magnitude (i.e., only the acceleration due to gravity), so b is false.

Uniform circular motion is a curvilinear motion in which the magnitude of acceleration does not change (but the direction keeps changing) and the magnitude of velocity (i.e., linear velocity) does not change, so c is false.

Same as option b, the parabolic motion is a curvilinear motion under the action of constant force (gravity), so d is wrong.

b correct aThe tangential acceleration must not be zero.

b.Normal acceleration must not be zero (except at the inflection point).

c.Since the velocity is in the tangential direction, the normal partial velocity must be zero, so the normal acceleration must be zero. --Non-Circular Motion

d.If the object moves at a uniform rate, its total acceleration must be zero. - Change in the direction of acceleration of circular motion

e.If the acceleration of an object is a constant vector, it must be moving at a uniform rate. --Flat Throwing Motion".

are all counterexamples.

b correct. The direction of velocity of an object moving along a curve must be constantly changing, and the normal acceleration is perpendicular to the direction of velocity and changes the direction of velocity.

Error in A B: The normal phase acceleration is zero when moving in a uniform circular motion C is not zero when the variable speed curve is moving, or the normal phase acceleration is always gd when throwing an object flat, and the topic does not say that it is cloud velocity motion.

e The acceleration is constant vector when moving in a uniform circular motion.

b.Normal acceleration must not be zero (except at the inflection point).

Methods for studying curvilinear motion: Synthesis and decomposition using the vectors of physical quantities such as velocity, displacement, acceleration, and force.

1) Curvilinear motion under the action of constant force: This motion is a uniform motion. Generally, the initial velocity of the moving object is decomposed along the direction of the force and the direction perpendicular to the force, and the object moves in a uniform linear motion along the direction of the force, and the object moves in a uniform linear motion in the direction perpendicular to the force.

If the direction and velocity and force are not in a straight line, the velocity and force are decomposed in the direction of the problem and perpendicular to the problem.

2) Curved motion under the action of variable force: this motion is a non-uniform variable speed motion. Generally, the force experienced by an object is decomposed in the direction of motion and in the direction perpendicular to the motion. A force that is consistent with the direction of motion changes the magnitude of velocity, and a force perpendicular to the direction of motion changes the direction of motion.

Examples of curvilinear movements in life.

Bullets shooting out of the breech, off-string arrows, throwing shot put, shooting, boats crossing rivers, etc., are all curved movements.

a. The object is thrown flat.

Displacements are vectors, and synthesis and decomposition follow the parallelogram rule.

Therefore, the displacement magnitude of the combined motion is not equal to the algebraic sum of the displacement magnitude of the two sub-motions, so a is wrong;

b. The object is in flat throwing motion, and the synthesis and decomposition of the displacement follow the parallelogram rule, so the displacement of the combined motion and the displacement of the two sub-motions just form a right triangle.

The combined displacement is hypotenuse, so b is correct;

c. The object is in flat throwing motion, the velocity is a vector, and the synthesis and decomposition follow the parallelogram rule, so the velocity of the combined motion is not equal to the algebraic sum of the velocity of the two sub-motions, so c is wrong;

d. The synthesis and decomposition of the velocity follow the parallelogram rule, so the velocity of the combined motion and the velocity of the two sub-motions just form a right-angled triangle, and the combined velocity is hypotenuse, which is greater than the sub-velocity, so D is wrong;

Therefore, b

The condition for an object to move in a curve is that the object is subjected to an external force that is not in the same line as the direction of motion (i.e., it cannot be the same or opposite to the direction of motion), such as a flat throwing motion, the initial velocity is horizontal, and it is subject to a vertical downward gravitational force so it will deflect in the direction of the force (that is, the vertical downward direction).

However, if the initial velocity of the object is zero, it has to be discussed separately, because the initial velocity is zero, then the direction of the resultant force is the same as the direction of motion, and it makes no sense to change the magnitude of the force, so it is necessary to require the direction of the force to change in order to form a curvilinear motion. For example, if a stationary ball first gives a force to the right, the ball will move to the right, and then the direction of the force will change to downward, and the object will do a curved motion similar to a flat throw.

For example, throwing the ball forward, regardless of air resistance, has a forward speed, but is affected by downward gravity, the speed is inconsistent with the direction of the force, and the curved motion is done. Another example.

Average velocity = displacement time.

Average speed = distance time.

In the curvilinear motion, the average speed of the jujube may be equal to zero;

In a curvilinear motion, the average rate cannot be equal to zero.

The magnitude of the average velocity is always less than or equal to the average velocity. (Because the magnitude of the displacements is always less than or equal to the distance.) ）

The average velocity is the ratio of the distance traveled by an object to the time taken to pass through that distance, and as long as the object moves, then the velocity will not be 0.

The average velocity is the ratio of the displacement of the object passing through and the time of passing through the displacement, when the object travels the bridge and returns to the origin, the displacement is 0, then the velocity is also 0.

The distance is a scalar quantity, the displacement is a vector quantity, and there must be a distance between two points, so the magnitude of the average velocity cannot be larger than the average velocity.

Option B; A false, counterexample: uniform circular motion.

B right, note: it can be considered that the inflection point is doing a uniform speed linear motion in a very short time, only the tangential acceleration c is wrong, and the counterexample: uniform circular motion.

D is false, counter-example: uniform circular motion (there is no such thing as "total acceleration") E false, counter-example: flat throwing motion, which is a uniform velocity motion, but not a uniform velocity motion (the difference between velocity and velocity).

A: False, such as uniform circular motion, tangential acceleration is 0

B: That's right. c: False, such as uniform circular motion, normal acceleration greater than 0d: false, such as uniform circular motion, total acceleration is equal to normal acceleration, greater than 0e: right, acceleration is unchanged, then the rate of change of velocity is the same.

Is the normal direction over the center of the circle?,If so, you should choose B.,The centripetal acceleration is not 0.。