A skydiver (a skydiver was training in low altitude diving and he left)

1. The title gives S+S2= 476m. Insert the known value of S2 into this formula to find the value of the total altitude S. Then calculate the speed V of the parachutist when opening the parachute according to the formula V=gt. Then consider the parachutist's movement time T in the air. According to the relationship between speed change and acceleration, we have T= V2Va, where a is the acceleration of deceleration and also takes a negative value to indicate deceleration. Insert the known values of V2V and a into the formula to find T; Because the athlete's speed is less than 0 at the moment of landing, which means that the upward force is greater than the downward force, A If is chosen;1 American skydiver Luke Akins successfully completed the event on July 30A skydiverIn a bold challenge, he jumped from an altitude of 7620 meters without using a parachute, but fell safely into the net prepared in advance, setting a world record. 2 The jump was broadcast live on Fox News Channel to the global audience. During the jump, 42-year-old Akins only wore an oxygen mask and a green jumpsuit without carrying it; It can be seen from the image that downward is positive, and the slope of the A speed-time image is equal to the acceleration. From the image, it can be seen that the slope from 0 to 10s is positive, the acceleration is downward, the slope from 10 to 15s is negative, and the acceleration is upward, so A is correct B It can be seen from the image that the slope gradually decreases within 0 to 10 s and 15s, so the accelerations gradually decrease. Therefore, B is correct C If you do uniformly accelerating straight line motion at 010s, the displacement is 100m, and the area enclosed by the image in this question is larger than uniformly accelerating straight motion. Therefore, it falls within 0 to 10 seconds; analysis 1 shows that when the parachute is opened, the speed of the athlete is v0=20 ms, and the falling distance is h0 ==20 m2. It can be seen from figure a that the skydiving athlete finally performs uniform movement, and its final speed is v=5 ms. Based on the balance conditions, kv=2mg, k=200 N·sm, the moment the parachute is opened, the total is k2mg =2ma, a===30 ms2, and the direction is vertical upward. 3 Set the tension of each rope as F, and land after opening.

2. Falling at a uniform speed, the object is balanced, and the resistance is greater than that of gravity. F resistance = Gtotal =800+20×10= 1000N; the front and back are divided into two motion states. The first is free falling motion. The acceleration at this time is g. After opening the umbrella, do uniform deceleration linear motion acceleration. The acceleration at this time is a. The v in both processes changes at all times. Regardless of this, the calculation formula for the distance in uniform acceleration and uniform deceleration motion is 12at^2 because; Analysis of 1000N After analyzing, the umbrella and the athlete are subjected to gravity and air resistance in the air. Because the umbrella and the athlete are descending at a uniform speed in the air, the joint external force experienced by the umbrella and the athlete is 0N, that is, gravity and air resistance are equal in magnitude and in opposite directions. From the meaning of the question, we know that G member = 800N, G umbrella =mg=20kg×10Nkg=200N, so air resistance F resistance =G member +G umbrella = 1000N. The definition and rules of the balance of the two forces are defined.

3. Question 2A skydiverYou can think of it this way. When you first jump, the parachute of the skydiver does not open. After that, the vertical direction is only affected by gravity. At this time, the air resistance is small and ignored. The downward acceleration is large, and the speed will become very fast. After a period of time, the parachute is opened, and the air resistance becomes significantly larger. The time during the parachute opening process is ignored. At this time, the acceleration is upward and the speed slowly decreases. As the speed; Shanxi skydivers unfurled the national flag in the air, which is to put the national flag down when skydiving. In fact, there are some heavy objects at the end of the national flag, so that a straight line can be supported on his feet and end. In this case, the national flag will float in the air. There is actually a string placed on his ankle at the upper end of the national flag. In this way, the national flag will look more stretched. Flying in the air is actually normal for us; Process analysis The moment the athlete parachutes, the resultant force is gravity, and the acceleration is at the maximum value and begins to fall. The speed starts to increase from 0. The resistance increases with the increase of speed. It is a variable acceleration movement in which the speed gradually increases and the acceleration gradually decreases. When the resistance controlled by speed is equal to gravity, the external force experienced by the athlete is zero. It is a uniform straight fall movement. Because the platform is high enough and the athlete opens the parachute while jumping away from the tower, that is to say.

4. Falling at a constant speed, balanced by force F=G=G=G person +m umbrella g= 800N +20kg * 10Nkg = 1000N; Answer: After leaving the plane, the athlete first performs free fall. As the falling distance increases and the speed increases, he will pull the parachute open at a certain moment and start to decelerate at a suitable height. He readjusted the parachute to keep it The entire process of descent at a suitable speed until landing requires precise control of time and altitude to ensure safety explains that the skydiving performance performed by a skydiver after leaving the plane is a highly technical task; Analysis shows that the umbrella and the athlete are descending at a uniform speed in the air, so the force exerted by the umbrella and the athlete is the balance force, that is, the gravity of the umbrella and the athlete is equal to the air resistance they experience. 1 The gravity of the umbrella and the athlete is because the umbrella and the athlete are doing uniform linear motion in the air. Therefore, the air resistance at this time is equal to the gravity of the umbrella and the athlete, that is, equal to 1000N, and the direction is vertical and upward. If the resistance is 1000N, the direction is vertical.

5. Balance of two forces = total gravity =1000 ~ I hope it will help you, please click the Accept as Satisfied Answer button in time ~~ Friends who ask questions on their mobile phones can be satisfied at the evaluation point in the upper right corner of the client ~~ Your adoption is my motivation for progress ~~ Landing.