"End of Chapter Review Lesson" Research on Uniform Speed ​​Linear Motion PPT

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"End of Chapter Review Lesson" Research on Uniform Speed ​​Linear Motion PPT

Part One: Consolidation Layer Knowledge Integration

[Core Quick Fill]

1. Laws of uniform speed linear motion

(1)Speed ​​formula: _________.

(2)Displacement formula: _________.

(3)Velocity-displacement relationship: _________.

2. Two important corollaries of uniform linear motion

(1) Average speed formula: v-=vt2=v0+vt2.

(2) The difference between the displacements within any two consecutive equal time intervals T is a constant, that is, ________.

3. free fall motion

(1) Properties of motion: initial velocity v0 = 0, acceleration is ________ motion of gravity acceleration g.

(2) Movement rules

①Speed ​​formula: vt=___________.

②Displacement formula: h=___________.

③Velocity-displacement relationship: v2t=____________.

Part Two: Upgrading to Ability Strengthening

Application of Laws of Uniform Speed ​​Linear Motion

To solve the problem of uniformly variable linear motion, common methods are summarized as follows:

Commonly used methods, rules and characteristics

General formula method The general formula method refers to the three formulas of velocity formula, displacement formula and velocity-displacement relationship. They are all vector types, so pay attention to directionality when using them. Generally, the direction of v0 is taken as the positive direction, the others that are the same as the positive direction are taken as positive, and those that are opposite to the positive direction are taken as negative.

The definition of the average speed method v=st is applicable to any type of motion, while v=12 (v0+vt) is only applicable to linear motion with uniform speed.

[One word to clear customs]

Optimal method for formula of uniformly variable linear motion

(1) Understand the characteristics and application scenarios of each uniformly variable linear motion formula.

(2) Carefully analyze the known conditions (present them in written form if necessary), see which formula the known conditions match the characteristics of, and then choose to use it.

(3) For uniformly variable linear motion problems that cannot be solved directly with a single formula, it is necessary to consider the combination of formulas from multiple angles and choose the best combination to solve the problem.

For training

1. An object moving in a straight line with uniform acceleration passes through two points A and B that are s apart, with velocities of v and 7v respectively. The movement time from A to B is t, then which of the following statements is incorrect ()

A. The speed passing through the midpoint of AB is 4v

B． The speed passing through the middle moment of AB is 4v

C. The time required for the s2 displacement before passing is twice the time required for the s2 displacement after passing

D． The displacement passed in the first t2 time is 1.5vt less than the displacement passed in the later t2 time

2. (Multiple choice) A car is driving along a straight road. There is a row of telephone poles parallel to the road next to the road. The distance between adjacent telephone poles is 50 m. Take the time when the car passes a certain telephone pole as the zero time, and this telephone pole is regarded as the first telephone pole. The speed of the car at this moment is v0 = 5 m/s. Assume that the movement of the car is a uniformly accelerated linear motion. At the end of 10 s, the car happens to pass the third telephone pole, then the correct one of the following statements is ()

A. The acceleration of the car's motion is 1 m/s2

B． The car continues to drive, and the instantaneous speed when passing the seventh telephone pole is 25 m/s

C. The time it takes for the car to move between the 3rd and 7th telephone poles is 20 s

D． The average speed of the car moving between the 3rd to 7th telephone poles is 20 m/s

Comparison of st image and vt image

[Example 2] In the displacement (s)-time (t) image and velocity (v)-time (t) image shown in the figure, the four curves 1, 2, 3, and 4 given represent the curves of four different objects. Movement conditions, regarding their physical meaning, the following description is correct ()

A. Figure 1 shows that the object moves in a curve

B． In the st image, v1>v2 at time t1

C. In the vt image, the average speeds of 3 and 4 from 0 to t3 are equal in size.

D． In the two images, moments t2 and t4 respectively indicate that 2 and 4 start to move in the opposite direction.

[One word to clear customs]

Moving image application skills

(1) Confirm which image it is, vt image or st image.

(2) Understand and memorize the five corresponding relationships.

①The slope corresponds to acceleration or speed;

②The longitudinal intercept corresponds to the initial velocity or initial position;

③The cross-intercept corresponds to the moment when the velocity or displacement is zero;

④The intersection points correspond to the same speed or position;

⑤The inflection point corresponds to a change in motion state.

Chasing encounter issues

Two objects moving on the same straight line often involve problems of catching up, meeting or avoiding collision. The key condition for answering such problems is: whether the two objects can reach a certain position in space at the same time.

1. Problem-solving methods for pursuit and encounter problems.

(1) Physical analysis method: Through the analysis of physical scenarios and physical processes, find the critical state and critical conditions, and then solve the equations. Pay special attention to "one condition and two relations". "One condition" is the critical condition that is satisfied when the speed is equal, and "two relationships" refer to the time relationship and the displacement relationship.

(2) Mathematical analysis method: The displacement relational expression of uniformly variable linear motion is a quadratic equation with respect to time. The method of finding the extreme value of a quadratic function can be used to determine the critical state.

(3) Image method: Solve with the help of vt image analysis.

2. The basic idea is:

(1) Study two objects separately.

(2) Draw a schematic diagram of the movement process.

(3) List the displacement equation.

(4) Find out the time relationship, speed relationship and displacement relationship.

(5) Solve the results and discuss if necessary.

[One word to clear customs]

Combining the meaning of the question to find the equivalent relationship between motion time, displacement and speed is the key to solving the problem.

7． A police car on duty was parked on the side of the road. When the police officer discovered that the truck driving next to him at a constant speed of 10 m/s was seriously overloaded, he decided to chase it. After 5.5 s, the police car started and started driving at a speed of 2.5 m/s. The acceleration of s2 is a uniform acceleration motion, but the driving speed of the police car must be controlled within 90 km/h. ask:

(1) When a police car is chasing a truck, what is the maximum distance between the two vehicles?

(2) Determine whether the police car can catch up with the truck during the acceleration phase? (Requires explanation through calculation)

(3) How long does it take for the police car to catch up with the truck after it starts?

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Update Time: 2024-09-22

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