To make a cylindrical tin bucket without a cover, the bottom diameter is 40cm, and the height of the bucket is 50cm. How many square centimeters of tin should be used to make such a bucket

To make a cylindrical tin bucket without a cover, the bottom diameter is 40cm, and the height of the bucket is 50cm. How many square centimeters of tin should be used to make such a bucket

40 △ 2 = 20cm 20 × 20 × 3.14 = 1256 square centimeter 40 × 3.14 × 50 = 6280 square centimeter
1256 + 6280 = 7536 square centimeter

As shown in the figure, the bucket has a mass of 2kg, a bottom area of 500cm2 and a height of 50cm. Place the bucket on the horizontal ground and pour 30kg water into the bucket. At this time, the distance from the water surface to the bottom of the bucket is 40cm. When Xiaoming lifts the bucket with a vertical upward force F, but does not lift it, the pressure of the bucket on the ground decreases by 3000pa. (g = 10N / kg) ask: (1) what is the size of F? (2) Before lifting the bucket, how much lower is the pressure of water on the bottom of the bucket than the pressure of the bucket on the ground? (3) After lifting the bucket, how much greater is the pressure of water on the bottom of the bucket than the pressure of the bucket on the ground?

(1) The tensile force F is: F = △ PS = 3000pa × 500 × 10-4m2 = 150n; (2) the pressure of water on the bottom of the bucket: pwater = ρ water, GH = 1 × 103kg / m3 × 10N / kg × 0.4m = 4000Pa, the pressure of the bucket on the ground: pdearth = FS = GS = (M bucket + m water) g & nbsp; s = (& nbsp; 2 kg + 30 kg) × 10 N / kg, 500 × 10 − 4 M2 = 6400 PA, so before lifting the bucket, the pressure of water on the bottom of the bucket is lower than that of the bucket on the ground: pdi-pwater = 6400 pa-4000 PA = 2400 Pa; (3) after lifting the bucket, the pressure of the bucket on the ground: PDI ′ = pdi-3000 PA = 3400 PA, and the pressure of water on the bottom of the bucket is higher than that of the bucket on the ground: PDI ′ - pwater = 4000 pa-3400 PA = 600 PA (2) before lifting the bucket, the pressure of water on the bottom of the bucket is 2400pa lower than that of the bucket on the ground; (3) after lifting the bucket, the pressure of water on the bottom of the bucket is 600Pa higher than that of the bucket on the ground