Four physics application problems need formula and process 1. When a car runs on a straight road, if it runs at a speed of 30 m / s, then it runs at a speed of 10 m / s to finish the rest 3 / 4, the average speed of the car in the whole journey can be calculated 2. A football flies to the ground at the speed of 10 m / s. when it is about to reach the ground, it is kicked out in the opposite direction by a football player, so that the football flies to the air along the original route at the speed of 20 m / s. if the time that the player plays with the ball is 0.1 s, the acceleration of the football in this process is tried 3. When the car starts to fight and advances with uniform acceleration for 10 s, it has walked 50 m in total. The acceleration of the car is calculated, and the total displacement of the car after it continues to accelerate for 5 s is obtained 4. A small ball falls freely from the edge of the roof, and the displacement in the last 1s before it reaches the ground is 9 / 25 of the height of the building

Four physics application problems need formula and process 1. When a car runs on a straight road, if it runs at a speed of 30 m / s, then it runs at a speed of 10 m / s to finish the rest 3 / 4, the average speed of the car in the whole journey can be calculated 2. A football flies to the ground at the speed of 10 m / s. when it is about to reach the ground, it is kicked out in the opposite direction by a football player, so that the football flies to the air along the original route at the speed of 20 m / s. if the time that the player plays with the ball is 0.1 s, the acceleration of the football in this process is tried 3. When the car starts to fight and advances with uniform acceleration for 10 s, it has walked 50 m in total. The acceleration of the car is calculated, and the total displacement of the car after it continues to accelerate for 5 s is obtained 4. A small ball falls freely from the edge of the roof, and the displacement in the last 1s before it reaches the ground is 9 / 25 of the height of the building

According to v2-v1 = at20 - (- 10) = a × 0.1, a = 300m / s and 178; 3. According to s = & 189; at & 178; a = 2S / T and 178; = 1m / s and 178; s ′ = & 178; at ′ & 178; = & 189; × 1 × 15 and 178; m = 112.5m4

Please pay formula and process unit for physical calculation
Xiao Ming used pulley block to lift the object weighing 900N from the first floor to the sixth floor at a constant speed, and the pulling force was 360n
The moving speed of the free end of the rope is 0.3m/s (the known height of each floor is 3M)
1. The time Xiao Ming spent
2. Power of pulling force
3. Extra work done
4. On this basis, add a pulley to make a new pulley block. When lifting the same weight, how will the mechanical efficiency of the pulley block change? Why?
The picture shows a pulley block with two pulleys and three pieces of rope pulled in the upper left direction

When the free end of the rope is 0.3m/s, the speed of the object is 0.1m/s, so the time taken is 3 * 5 / 0.1s = 150s (one to six layers only need to go up 15m). The pulling power P = 360 * 0.3w = 108W. The extra work done should be the work done by the force of three strands of rope pulling the pulley, this force = 3

Find the formula and answer of two practical problems
1. A steel pipe is 3 / 4 meters long, and 8 / 9 of it is sawed off. How long is the sawed off part?
2. A rope is four fifths of a meter long. One half of it is used for the first time. One half of it is used for the second time. How many meters are used for the second time?

1. 3 / 4 times 8 / 9 is 2 / 3 meter
2. Four out of five times one out of two times one out of two equals one out of five meters

Two practical problems (formula, process and result)
(1) In a certain grade, 120 students signed up for the math interest group, which is 20% more than the number of the planned interest group. How many students did the planned interest group accept?
(2) 6 kg is 20% more than 5 kg, and how much less than 5 kg?

1. 120 (1 + 20%) = 100 persons
2. 1-5 △ 6 = 17%