In the experiment, how to determine whether the trajectory is a parabola is studied

In the experiment, how to determine whether the trajectory is a parabola is studied

Take the track map, divide the track in the horizontal direction, and then measure the vertical distance between the points. If the ratio of the two adjacent distances is 1:3:5:7 Or the distance ratio from each point to the first point is 1:4:9:16 : n ^ 2, then it is a parabola
Generally speaking, in the normal vertical gravitational field, without considering the resistance factor, the trajectory of horizontal projectile must be parabolic

Pole vault is a highly technical sport. The whole process can be simplified into three stages as shown in the figure: run-up with pole, take-off with pole and fall over the pole. In the 29th Beijing Olympic Games, Isinbayeva, a 1.74m Russian female athlete, broke the world record with a score of 5.05m. Let Isinbayeva accelerate the run-up distance evenly from static state s = 3 When the speed reaches 8.0 M / s, the strut will take off and make the center of gravity rise H 1 = 4.20 m, then cross the cross bar. When the center of gravity falls H 2 = 4.05 m, the body will contact the cushion, and the horizontal displacement from the highest point to the landing is x = 0.9 M (1) (2) if Isinbayeva only transforms the kinetic energy provided by the run-up into the gravitational potential energy in the process of rising by means of the brace, how much can she make her center of gravity rise at most? (3) How much work does Isinbayeva have to do at least in the rising stage of pole vault?

(1) Suppose the run-up distance is s, the kinematics formula V2 = 2As is used to solve the problem, and a = 1m / S2 (2) according to the conservation of mechanical energy, there is: 12mv2 = MGH, and the solution is h = 3.2 & nbsp; M (3) suppose that the horizontal speed of the athlete at the highest point is VX, and the athlete does horizontal throwing in the falling stage, H 2 = 12gt2x = vxt, the solution is v = 1.0m/s, and the work done in the rising stage of the take-off strut is w. the functional relationship is: W + 12mv 02 = MGH 1 + 12mv & nbsp; The solution of 2x is: e = 683j A: (1) the acceleration of Isinbayeva's uniform acceleration run-up is 1mgs2; (2) if Isinbayeva only transforms the kinetic energy provided by the run-up into the gravitational potential energy in the rising process with the help of the pole, she can raise her gravity center by 3.2m at most; (3) Isinbayeva should do at least 683j work in the rising stage of the pole take-off

A physics problem (Sports)
The motorcycle starts to move in a straight line with a constant acceleration of A1 = 1 from a standstill. After a certain distance, it moves in a straight line with a constant speed. Then it moves in a straight line with a constant deceleration of A2 = 4 until it stops. It has driven 1750 meters in total and lasted for 100 seconds
(1) Maximum speed of motorcycle
(2) If the values of A1 and A2 remain unchanged, what is the shortest time required to travel this distance,

1) The maximum speed is 20m / S (2) the shortest time is 25 times root sign 7 seconds, the maximum speed is 20 times root sign 7 meters / s. The answer is a bit strange, but it should be like this This (1) if the acceleration time is a, the uniform speed time is B, and the deceleration time is C, then a = 4C, a + B + C = 100

A physics problem about motion
Before a train arrives at the station, it decelerates evenly and moves in a straight line. After starting to brake, the displacement in the 5th second is 57.5m, and the displacement in the 10th second is 32.5m. What is the acceleration of the train

According to the topic lesson, the speed of 4.5 seconds and 9.5 seconds are 57.5 and 32.5 respectively, and the acceleration a = (32.5-57.5) / (9.5-4.5) = - 5 m / s. The key here is to see the topic meaning. The fifth second is not the first five seconds, so the displacement is only one second