If the radius of the ball is r, then the volume of the ball is calculated by the formula v = four-thirds R. when the volume v = 500 cubic centimeters, what is the radius r?

V=4/3πr³
50=4/3πr³
r³=50x3/4xπ
=37.5π
=117.75
R = 4.9 cm

The radius of the ball is r cm, and the volume of the ball is 500 cubic cm (the volume formula of the ball is v = 4 / 3 of R's Cube). When the integer is 3, the radius of the ball is r =?

V = 4 / 3 cube of R = 4R ^ 3 = 500
R^3=125
R=5

The bottom of an isosceles right triangle is 5cm. What's its area?
How to do it!

The bottom is five
The right angle side is five times two
The area is the square of the right side divided by 2 = 25 / 4

An object with a mass of 2kg is placed on the horizontal floor, and a light spring is used to pull the object horizontally. When the object starts to move, the spring is extended by 3cm. When the object is pulled forward at a constant speed, the spring is extended by 2cm. It is known that the stiffness coefficient of the spring is k = 200N / m, and G is taken as 10m / S2? (2) What is the sliding friction factor between the object and the floor?

(1) According to Hooke's law, there is F1 = kx1 = 200N / m × 0.03m = 6N, so the maximum static friction force on the object is FF1 = 6N (2) when the object moves at a constant speed, the friction force on the object is sliding friction force, which is known from the balance of two forces and is equal to the spring force at this time, According to Hooke's law, there is F2 = kx2 = 200N / m × 0.02M = 4N, so the sliding friction force on the object is FF2 = 4N, and there is & nbsp; FF2 = μ Mg & nbsp; & nbsp; μ = 0.2 A: (1) the maximum static friction force on the object is 6N. (2) the dynamic friction coefficient between the object and the floor is 0.2

I haven't learned equation, so I use simple addition, subtraction, multiplication and division
Mr. Zhang bought 5 football and 12 basketball, a total of 330 yuan. The price of a football is equal to the price of two basketball, how much is each football? How much is each basketball?

One football is equal to two basketball, five football is equal to ten basketball
Therefore, each basketball: 330 ÷ (10 + 12) = 15 (yuan), each football: 15 × 2 = 30 (yuan)

If an object with a gravity of 100N is pulled horizontally by 20n and advances at a constant speed of 5m on the horizontal plane, the work done by gravity is J. The work done by pulling force is J．

① The object with a gravity of 100N advances at a constant speed of 5m on the horizontal plane. Although it is powerful and has a distance, it does not work because of F ⊥ S. therefore, the answer is: 0. ② the object is subject to a horizontal tension of 20n and advances at a constant speed of 5m on the horizontal plane. It has two conditions to do work, so the tension does work, ⊥ w = FS = 20n × 5m = 100J, so the answer is: 100

If A2 + A8 + a11 = 30, then S13=______ ．

From the properties of arithmetic sequence, we can get: A2 + a11 = A6 + A7, so A2 + A8 + a11 = A6 + A7 + A8 = 30, that is, 3a7 = 30, a7 = 10, so S13 = 13 (a1 + A13) 2 = 13 × 2a72 = 130, so the answer is: 130

If T1 / | T1 | + T2 / | T2 | + T3 / | T3 | = 1, then | t1t2t3 | / t1t2t3 |=

-1

After learning the multiplication and division of rational numbers, Xiao Gang wrote a calculation program. When he entered any rational number, the result on the screen was always - 1 / 2 divided by the sum of the entered number and its absolute value. However, when he tried to enter a number, the error message was displayed on the screen. The number he entered was --------, and the reason for the error message was -------

After learning the multiplication and division of rational numbers, Xiao Gang wrote a calculation program. When he entered any rational number, the result on the display screen was always equal to - 1 / 2 divided by the sum of the entered number and its absolute value. But when he tried to enter a number, the error message was displayed on the screen. The number he entered was 0, and the reason for the error message was that 0 could not be divided

The equation 5 (x + 3K) - 2 = 3x-4k has (1) positive solutions and (2) negative solutions

The equation is reduced to 2x = - 19K + 2
1)K2/19

If the radius of the ball is r, then the volume of the ball is calculated by the formula v = four-thirds R. when the volume v = 500 cubic centimeters, what is the radius r?