Chapter 12: Surface Areas and Volumes
Class 10 Standard Mathematics (Case Study Bank)
Curated By Akash Srivastva
Capsule-Shaped Smart Drug Delivery Vehicle
A smart drug-delivery capsule has a cylindrical center with two identical hemispherical ends:
• Total length: \(12\text{ mm}\)
• Capsule diameter: \(6\text{ mm}\) (radius \(r = 3\text{ mm}\))
• Parameter: Take \(\pi = 3.14\)
📋 View Step-by-Step Marking Scheme & Solution▼
| Question | Expected Answer / Step-by-Step Solution | CBSE Marks Allocation |
|---|---|---|
| Q1 | r = 6/2 = 3 mm. Cylindrical height h = 12 − 2(3) = 6 mm. CSA = 2πrh = 2 × 3.14 × 3 × 6 = 113.04 mm². |
[0.5 Mark] for h = 6 mm. [0.5 Mark] for CSA = 113.04 mm². |
| Q2 | TSA = 2πrh + 2(2πr²) = 2πr(h + 2r) = 2 × 3.14 × 3 × (6 + 6) = 226.08 mm². | [1 Mark] for TSA = 226.08 mm². |
| Q3 | V = πr²h + 2(2/3 πr³) = πr²(h + 4/3 r) = 3.14 × 9 × (6 + 4) = 282.6 mm³. | [1 Mark] for volume formula setup. [1 Mark] for 282.6 mm³. |
| Q3 (OR) | New h = 10 − 6 = 4 mm. V_new = 3.14 × 9 × (4 + 4) = 226.08 mm³. Reduction = 282.6 − 226.08 = 56.52 mm³. % Reduction = (56.52 / 282.6) × 100% = 20%. |
[1 Mark] for new volume. [1 Mark] for 20% reduction. |
Double-Walled Thermal Flask
A double-walled stainless steel thermal flask combines a cylinder and a conical neck with common radius \(r = 7\text{ cm}\):
• Cylinder height: \(h_{\text{cyl}} = 10\text{ cm}\)
• Cone height: \(h_{\text{cone}} = 24\text{ cm}\)
• Parameter: Take \(\pi = \frac{22}{7}\)
📋 View Step-by-Step Marking Scheme & Solution▼
| Question | Expected Answer / Step-by-Step Solution | CBSE Marks Allocation |
|---|---|---|
| Q1 | l = √(r² + h_cone²) = √(7² + 24²) = √625 = 25 cm. | [1 Mark] for l = 25 cm. |
| Q2 | CSA_cone = πrl = (22/7) × 7 × 25 = 550 cm². | [1 Mark] for 550 cm². |
| Q3 | V = πr²h_cyl + 1/3 πr²h_cone = (22/7) × 49 × (10 + 8) = 154 × 18 = 2772 cm³. | [1 Mark] for formula setup. [1 Mark] for 2772 cm³. |
| Q3 (OR) | CSA_cyl = 2 × (22/7) × 7 × 10 = 440 cm². Total CSA = 440 + 550 = 990 cm². | [1 Mark] for cylinder CSA. [1 Mark] for total CSA = 990 cm². |
Rocket Booster Payload Fairing
A rocket payload fairing has a lower cylindrical booster section and a conical nose cone with common radius \(r = 5\text{ m}\):
• Cylinder height: \(h_{\text{cyl}} = 20\text{ m}\)
• Nose cone height: \(h_{\text{cone}} = 12\text{ m}\)
• Parameter: Take \(\pi = 3.14\)
📋 View Step-by-Step Marking Scheme & Solution▼
| Question | Expected Answer / Step-by-Step Solution | CBSE Marks Allocation |
|---|---|---|
| Q1 | l = √(5² + 12²) = √169 = 13 m. | [1 Mark] for l = 13 m. |
| Q2 | Outer Area = 2πrh_cyl + πrl = 3.14 × 5 × (2(20) + 13) = 15.7 × 53 = 832.1 m². | [1 Mark] for 832.1 m². |
| Q3 | V = πr²h_cyl + 1/3 πr²h_cone = 3.14 × 25 × (20 + 4) = 78.5 × 24 = 1884 m³. | [1 Mark] for formula setup. [1 Mark] for 1884 m³. |
| Q3 (OR) | V_hemi = 3.14 × 25 × (20 + 10/3) = 1831.67 m³. Difference = 1884 − 1831.67 = 52.33 m³. |
[1 Mark] for hemispherical volume. [1 Mark] for difference = 52.33 m³. |
Artisanal Ice Cream Treat
A confectioner's ice cream treat consists of a hemispherical scoop atop a conical waffle sleeve:
• Common radius: \(r = 3\text{ cm}\)
• Cone height: \(h = 4\text{ cm}\)
• Parameter: Take \(\pi = 3.14\)
📋 View Step-by-Step Marking Scheme & Solution▼
| Question | Expected Answer / Step-by-Step Solution | CBSE Marks Allocation |
|---|---|---|
| Q1 | l = √(3² + 4²) = 5 cm. CSA = πrl = 3.14 × 3 × 5 = 47.1 cm². | [0.5 Mark] for l = 5 cm. [0.5 Mark] for CSA = 47.1 cm². |
| Q2 | Exposed Area = 2πr² = 2 × 3.14 × 9 = 56.52 cm². | [1 Mark] for 56.52 cm². |
| Q3 | V = 1/3 πr²(2r + h) = 1/3 × 3.14 × 9 × (6 + 4) = 3.14 × 3 × 10 = 94.2 cm³. | [1 Mark] for volume setup. [1 Mark] for 94.2 cm³. |
| Q3 (OR) | V_cone = 1/3 π(3²)(8) = 24π cm³. V_hemi = 2/3 π(3³) = 18π cm³. Ratio = 24π / 18π = 4/3 = 4 : 3. |
[1 Mark] for component volumes. [1 Mark] for ratio 4 : 3. |
Circular Safari Glamping Tent
A glamping tent combines a cylindrical wall with a conical roof on a common radius \(r = 7\text{ m}\):
• Cylinder height: \(h_1 = 10\text{ m}\)
• Cone roof height: \(h_2 = 24\text{ m}\)
• Parameter: Take \(\pi = \frac{22}{7}\)
📋 View Step-by-Step Marking Scheme & Solution▼
| Question | Expected Answer / Step-by-Step Solution | CBSE Marks Allocation |
|---|---|---|
| Q1 | l = √(r² + h₂²) = √(7² + 24²) = √625 = 25 m. | [1 Mark] for l = 25 m. |
| Q2 | CSA_cyl = 2πrh₁ = 2 × (22/7) × 7 × 10 = 440 m². | [1 Mark] for 440 m². |
| Q3 | CSA_cone = πrl = (22/7) × 7 × 25 = 550 m². Total Canvas = 440 + 550 = 990 m². | [1 Mark] for cone CSA. [1 Mark] for 990 m². |
| Q3 (OR) | V_cyl = (22/7) × 49 × 10 = 1540 m³. V_cone = 1/3 × (22/7) × 49 × 24 = 1232 m³. Total Volume = 1540 + 1232 = 2772 m³. |
[1 Mark] for component volumes. [1 Mark] for 2772 m³. |
Industrial Grain Storage Silo
An industrial grain silo consists of a cylindrical tank with a bottom conical hopper on common radius \(r = 3.5\text{ m}\) (\(\frac{7}{2}\text{ m}\)):
• Cylinder tank height: \(h_1 = 20\text{ m}\)
• Hopper cone height: \(h_2 = 12\text{ m}\)
• Parameter: Take \(\pi = \frac{22}{7}\)
📋 View Step-by-Step Marking Scheme & Solution▼
| Question | Expected Answer / Step-by-Step Solution | CBSE Marks Allocation |
|---|---|---|
| Q1 | l = √((3.5)² + 12²) = √(12.25 + 144) = √156.25 = 12.5 m. | [1 Mark] for l = 12.5 m. |
| Q2 | V_hopper = 1/3 × (22/7) × (7/2)² × 12 = 22 × 7 = 154 m³. | [1 Mark] for 154 m³. |
| Q3 | V_cyl = (22/7) × (7/2)² × 20 = 770 m³. Total Volume = 770 + 154 = 924 m³. | [1 Mark] for cylinder volume. [1 Mark] for total = 924 m³. |
| Q3 (OR) | CSA_cyl = 2 × (22/7) × (7/2) × 20 = 440 m². CSA_cone = (22/7) × (7/2) × 12.5 = 137.5 m². Total Area = 440 + 137.5 = 577.5 m². |
[1 Mark] for area components. [1 Mark] for 577.5 m². |
Boiling Flask Calibration
A round-bottom laboratory boiling flask combines a spherical bulb with a cylindrical neck:
• Spherical bulb radius: \(R = 10.5\text{ cm}\) (\(\frac{21}{2}\text{ cm}\))
• Cylindrical neck: radius \(r = 3.5\text{ cm}\) (\(\frac{7}{2}\text{ cm}\)), height \(h = 8\text{ cm}\)
• Parameter: Take \(\pi = \frac{22}{7}\)
📋 View Step-by-Step Marking Scheme & Solution▼
| Question | Expected Answer / Step-by-Step Solution | CBSE Marks Allocation |
|---|---|---|
| Q1 | CSA_neck = 2πrh = 2 × (22/7) × (7/2) × 8 = 176 cm². | [1 Mark] for 176 cm². |
| Q2 | V_neck = πr²h = (22/7) × (7/2)² × 8 = 308 cm³. | [1 Mark] for 308 cm³. |
| Q3 | V_sphere = 4/3 × (22/7) × (21/2)³ = 11 × 441 = 4851 cm³. Total = 4851 + 308 = 5159 cm³. | [1 Mark] for spherical volume. [1 Mark] for 5159 cm³. |
| Q3 (OR) | 4500 cm³ < 5159 cm³, so it will NOT overflow. Empty volume = 5159 − 4500 = 659 cm³. | [1 Mark] for overflow verdict. [1 Mark] for 659 cm³. |
Historic Gateway Pillar Restoration
A heritage solid sandstone gateway pillar combines a cylinder surmounted by a hemispherical dome of radius \(r = 21\text{ cm}\):
• Cylinder height: \(h = 50\text{ cm}\)
• Parameter: Take \(\pi = \frac{22}{7}\)
📋 View Step-by-Step Marking Scheme & Solution▼
| Question | Expected Answer / Step-by-Step Solution | CBSE Marks Allocation |
|---|---|---|
| Q1 | Total height H = h + r = 50 + 21 = 71 cm. | [1 Mark] for H = 71 cm. |
| Q2 | CSA_dome = 2πr² = 2 × (22/7) × 21 × 21 = 2772 cm². | [1 Mark] for 2772 cm². |
| Q3 | V_cyl = (22/7) × 21² × 50 = 69,300 cm³. V_hemi = 2/3 × (22/7) × 21³ = 19,404 cm³. Total Volume = 69,300 + 19,404 = 88,704 cm³. |
[1 Mark] for component volumes. [1 Mark] for 88,704 cm³. |
| Q3 (OR) | CSA_cyl = 2 × (22/7) × 21 × 50 = 6600 cm². Total Polishing Area = 6600 + 2772 = 9372 cm². |
[1 Mark] for cylinder CSA. [1 Mark] for 9372 cm². |