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If h,s V be the height , curved surface ...

If h,s V be the height , curved surface area and volume of a cone respectively , then ` ( 3pi Vh^(3) + 9V^(2) -s^(2) h^(2))` is equal to :

A

0

B

`pi `

C

`(V)/(sh)`

D

`(36)/(V)`

Text Solution

AI Generated Solution

The correct Answer is:
To solve the problem, we need to analyze the relationship between the height (h), curved surface area (s), and volume (V) of a cone. ### Step-by-Step Solution: 1. **Identify the formulas for volume and curved surface area of a cone:** - The volume \( V \) of a cone is given by: \[ V = \frac{1}{3} \pi r^2 h \] - The curved surface area \( s \) of a cone is given by: \[ s = \pi r l \] where \( l \) is the slant height, calculated as: \[ l = \sqrt{h^2 + r^2} \] 2. **Substituting the volume into the expression:** - We need to evaluate the expression: \[ 3\pi V h^3 + 9V^2 - s^2 h^2 \] - Substitute \( V \) into the expression: \[ 3\pi \left(\frac{1}{3} \pi r^2 h\right) h^3 + 9\left(\frac{1}{3} \pi r^2 h\right)^2 - s^2 h^2 \] 3. **Simplifying the first term:** - The first term simplifies as follows: \[ 3\pi \left(\frac{1}{3} \pi r^2 h\right) h^3 = \pi^2 r^2 h^4 \] 4. **Simplifying the second term:** - The second term simplifies as follows: \[ 9\left(\frac{1}{3} \pi r^2 h\right)^2 = 9 \cdot \frac{1}{9} \pi^2 r^4 h^2 = \pi^2 r^4 h^2 \] 5. **Substituting for \( s \):** - Now substitute \( s \) into the expression: \[ s = \pi r l = \pi r \sqrt{h^2 + r^2} \] - Therefore, \( s^2 \) becomes: \[ s^2 = \pi^2 r^2 (h^2 + r^2) \] 6. **Substituting \( s^2 \) into the expression:** - Now we have: \[ \pi^2 r^2 h^4 + \pi^2 r^4 h^2 - \pi^2 r^2 (h^2 + r^2) h^2 \] 7. **Expanding the last term:** - The last term expands to: \[ \pi^2 r^2 (h^2 + r^2) h^2 = \pi^2 r^2 h^4 + \pi^2 r^4 h^2 \] 8. **Combining all terms:** - Now combine all the terms: \[ \pi^2 r^2 h^4 + \pi^2 r^4 h^2 - (\pi^2 r^2 h^4 + \pi^2 r^4 h^2) = 0 \] ### Final Result: Thus, the expression simplifies to: \[ 0 \] ### Conclusion: The final answer is \( 0 \).
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Knowledge Check

  • If h,s, V be the height, curved surface area and volume of a cone respectively, then (3 pi Vh^3 + 9V^2 -s^2h^2) is equal to

    A
    0
    B
    `pi`
    C
    V/(sh)
    D
    (36)/V
  • If surface area and volume of a sphere are S and V respectively, then value of (S^(3))/(V^(2)) is

    A
    `36 pi` units
    B
    `9 pi` units
    C
    `18 pi` units
    D
    `27 pi` units
  • Let h, s and v be height, curved surface area and volume, respectively, of a cone. If 3pivh^(3)-s^(2)h^(2)+kv^(2)=0 , then value of k is

    A
    3
    B
    6
    C
    9
    D
    12
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