Math

a hollow metal sphere has an internal radius of 20cm and an external radius of 30cm , given that the density of the metal is 7.8, find the mass of the sphere , expressing your answer in kg.

  1. 👍 0
  2. 👎 0
  3. 👁 794
  1. just multiply the volume of metal by its density to get the mass:

    cm^2 * g/cm^3 = g

    You know that the volume of a sphere of radius r is

    v = 4/3 πr^3

    so, to get the volume of metal, just subtract the volume of the empty inner sphere from the outer sphere.

    1. 👍 1
    2. 👎 0
  2. the volume of metal is
    ... v = 4/3 * π * (30³ - 20³) cm³

    if the density units are g/cm³
    then multiply v by .0078

    1. 👍 0
    2. 👎 1

Respond to this Question

First Name

Your Response

Similar Questions

  1. calculus

    3. The radius r of a sphere is increasing at a constant rate of 0.04 centimeters per second. (Note: The volume of a sphere with radius r is v=4/3pir^3 ). a. At the time when the radius of the sphere is 10 cm, what is the rate of

  2. Math

    A cone is constructed by cutting a sector from a circular sheet of metal with radius 20cm. The cut sheet is then folded up and welded. Find the radius and height of the cone with the maximum volume that can be formed in this way.

  3. calculus

    1. The radius of a sphere is r inches at time t seconds. Find the radius when the rates of increase of the surface area and the radius are numerically equal. A 1/4π in B 1/5π in C 1/3π in D 1/8π in E 1/2π in

  4. Physics

    The figure(Figure 1) shows a solid metal sphere at the center of a hollow metal sphere. Assume that E=1.2×104N/C. What is the total charge on the exterior of the inner sphere?

  1. College Physics

    Metal sphere 1 has a positive charge of 7.00nC . Metal sphere 2, which is twice the diameter of sphere 1, is initially uncharged. The spheres are then connected together by a long, thin metal wire. What are the final charges on

  2. MATHS

    A CYLINDRICAL PIPE MADE OF METAL IS 3 CM THICK .IF THE INTERNAL RADIUS OF THE PIPE IS 10 CM, FIND THE VOLUME OF THE METAL USED IN MAKING 3M OF THE PIPE RADIUS OF INTERNAL PIPE =10CM RADIUS OF EXTERNAL PIPE =13CMVOLUME OF PIPE=PI

  3. Physics

    A hollow sphere has a mass of 15 kg, an inner radius of 12 cm and an outer radius of 18 cm. What is the rotational inertia (moment of inertia) of the sphere about an axis passing through its center?

  4. Physics

    A solid metal ball and a hollow plastic ball of the same external radius are released from rest in a large vacuum chamber. When each has fallen 1 m, they both have the same 1. momentum. 2. inertia. 3. speed. 4. change in potential

  1. physics (please check work)

    Four identical particles, each with mass m, are arranged in the x,y plane like a cross. They are connected by light sticks to form a rigid body. If m=2.0kg and a=1.0 m the rotational inertia of this array about the y axis is:

  2. math

    A balloon in the shape of a sphere is deflating. Given that t represents the time, in minutes, since it began losing air, the radius of the ballon (in cem) is r(t)=16-t. Let the equation V(r)= 4/3 pi r^3 represent the volume of a

  3. Solid Mechanics

    Determine the ratio of strenghts of a solid steel column to that a hollow column of the same material and having the same cross sectional area. The internal diameter of the hollow column is 1/2 of its external diameter. Both the

  4. physics 12

    A hollow sphere us charged to 14uc .Find the potential(a) at its surface (b) inside the sphere (c) at a distance of 0.2m from the surface.The radius of sphere is 0.3 m

You can view more similar questions or ask a new question.