3D Shapes: Properties and Symmetry

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Questions and Answers

Which of the following statements accurately describes a key difference between 2D and 3D shapes?

  • 3D shapes have length, width, and height, while 2D shapes only have length and width. (correct)
  • 2D shapes have volume, while 3D shapes do not.
  • 3D shapes can only be represented on a computer, whereas 2D shapes can be drawn by hand.
  • 2D shapes take up space, while 3D shapes do not.

A solid figure has 6 faces, 12 edges, and 8 vertices. Which of the following could it be?

  • Cone
  • Triangular prism
  • Cube (correct)
  • Square-based pyramid

A sculptor creates a statue that remains unchanged after multiple rotations around a central axis. Which shape does this statue most likely resemble?

  • Cone
  • Cylinder (correct)
  • Rectangular Prism
  • Cube

A cube is sliced in half such that the two resulting pieces are identical. How many planes of symmetry does the original cube have?

<p>9 (C)</p> Signup and view all the answers

An architect is reviewing blueprints for a cylindrical pillar in a new building. Which view would show the height of the pillar?

<p>Front View (B)</p> Signup and view all the answers

An engineer needs to represent a complex machine component in a 2D drawing. What is the primary purpose of using multiple drawing views (top, front, and side)?

<p>To fully describe the 3D shape of the component. (B)</p> Signup and view all the answers

A map uses a scale of 1 inch = 5 miles. If two towns are 3.5 inches apart on the map, what is the actual distance between them?

<p>17.5 miles (B)</p> Signup and view all the answers

A blueprint for a garden uses a scale of 1:20. If the length of the garden on the blueprint is 25 cm, what will the actual length of the garden be in meters?

<p>5 meters (C)</p> Signup and view all the answers

A cylindrical tank has a radius of 4 meters and a height of 10 meters. What is the surface area of the tank?

<p>$112\pi ext{ m}^2$ (D)</p> Signup and view all the answers

If the radius of a cylinder is doubled while the height remains constant, how does the surface area change?

<p>The surface area will more than quadruple. (C)</p> Signup and view all the answers

A rectangular prism has a base area of 36 cm and a height of 8 cm. What is the volume of the prism?

<p>288 cm (D)</p> Signup and view all the answers

What is the volume of a cylinder with a radius of 6 cm and a height of 5 cm?

<p>$180\pi ext{ cm}^3$ (A)</p> Signup and view all the answers

A cylindrical container has a volume of 2000 cm. How many liters of liquid can it hold?

<p>2 L (C)</p> Signup and view all the answers

A tank has a volume of 7,500 cm. How many liters of water can it hold?

<p>7.5 L (D)</p> Signup and view all the answers

A rectangular prism has dimensions length = 8 cm, width = 5 cm, and height = 4 cm. What is its volume?

<p>160 cm (A)</p> Signup and view all the answers

A scale drawing of a park has a scale of 1:2000. If a path is 5 cm long on the drawing, what is the actual length of the path in meters?

<p>100 meters (D)</p> Signup and view all the answers

A cylinder has a surface area of $80\pi ext{ cm}^2$ and a radius of 4 cm. What is the height of the cylinder?

<p>6 cm (B)</p> Signup and view all the answers

A water tank in the shape of a rectangular prism has dimensions of 2m x 3m x 1.5m. How many liters of water can the tank hold when full?

<p>9,000 L (C)</p> Signup and view all the answers

If the dimensions of a rectangular prism are doubled, what is the effect on its volume?

<p>The volume increases by a factor of eight. (D)</p> Signup and view all the answers

A solid metal cylinder is melted down and recast into a sphere of the same volume. How does the volume of the cylinder compare to the volume of the sphere?

<p>The volume of the cylinder is equal to the volume of the sphere. (B)</p> Signup and view all the answers

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Flashcards

What are 3D Shapes?

3D shapes possess length, width, and height, occupying space and comprising faces, edges, and vertices.

Plane Symmetry

A 3D shape divided into two identical halves showcases this property.

Rotational Symmetry

A 3D object exhibits this when it appears unchanged after rotation.

Scale Drawings

Scaled representations of real objects, either proportionally smaller or larger than their actual size.

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Scale Factor

The ratio between the size of a scale drawing and the actual size of the object.

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Cylinder Surface Area Formula

SA = 2πr² + 2πrh, where r is the radius and h is the height.

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Prism Volume Formula

Volume = Base Area × Height

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Cylinder Volume Formula

Volume = πr²h, where r is the radius and h is the height.

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What is Capacity?

The amount of liquid a 3D shape can hold, measured in liters (L) or milliliters (mL).

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Volume to Capacity Conversion

1 cm³ = 1 mL; 1,000 cm³ = 1 L

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Study Notes

  • 3D shapes possess length, width, and height, occupying space and featuring faces, edges, and vertices.

Geometric Properties of 3D Shapes

  • A cube has 6 faces, 12 edges, and 8 vertices.
  • A rectangular prism has 6 faces, 12 edges, and 8 vertices.
  • A triangular prism has 5 faces, 9 edges, and 6 vertices.
  • A cylinder has 3 faces, 2 curved edges, and no vertices.
  • A sphere has 1 curved face, no edges, and no vertices.
  • A cone has 2 faces, 1 curved edge, and 1 vertex.
  • A square-based pyramid has 5 faces, 8 edges, and 5 vertices.

Symmetry in 3D Objects

  • Symmetry is when a shape or object can be divided into mirror images.

Plane Symmetry (Reflection Symmetry)

  • A plane of symmetry divides a 3D shape into two identical halves.
  • A cube has 9 planes of symmetry.
  • A cylinder has infinite planes of symmetry if cut vertically.

Rotational Symmetry

  • A 3D object has rotational symmetry if it appears the same after being rotated by a certain angle.
  • A sphere has infinite rotational symmetry.
  • A cube has rotational symmetry of order 4 around its vertical axis.
  • A cylinder has infinite rotational symmetry around its vertical axis.

Drawing Views of 3D Objects

  • Drawing views represent 3D objects in 2D, used in design by engineers and architects.

Types of Views

  • Top View (Plan View) illustrates the object from above.
  • Front View (Elevation View) illustrates the object from the front.
  • Side View: Shows what the object looks like from the side.
  • Views for complex shapes can vary in shape and size.
  • A cube's top, front, and side views are all squares.

Scale Drawings

  • A scale drawing represents an actual object proportionally, either smaller or larger than its real size.
  • The scale factor is the ratio between the drawing's size and the object's actual size.
  • Example: A 3 cm wall on a 1:50 scale blueprint represents an actual height of 1.5 meters (150 cm).

Types of Scale Factors

  • Enlargement (Scale Factor > 1) makes the object bigger.
  • Reduction (Scale Factor < 1) shrinks the object.

Surface Area of Cylinders

  • The surface area of a cylinder is calculated using the formula: SA = 2Ï€r² + 2Ï€rh, where r = radius, h = height.
  • Example: A cylinder with radius 5 cm and height 10 cm has a surface area of approximately 471.24 cm².

Volume of Prisms and Cylinders

  • The volume of a prism is calculated by multiplying the base area by the height: V = Base Area × Height.
  • Example: A rectangular prism with length 6 cm, width 4 cm, and height 10 cm has a volume of 240 cm³.
  • The volume of a cylinder is calculated using the formula: V = Ï€r²h, where r = radius, h = height.
  • Example: A cylinder with radius 3 cm and height 7 cm has a volume of approximately 197.92 cm³.

Volume and Capacity Relationships

  • Capacity measures the amount of liquid a 3D shape can hold, in liters (L) or milliliters (mL).
  • 1 cm³ equals 1 mL, and 1,000 cm³ equals 1 L.
  • A tank with a volume of 5,000 cm³ can hold 5 L of water.

Key Formulas

  • Surface Area of a Cylinder: SA = 2Ï€r² + 2Ï€rh
  • Volume of a Rectangular Prism: V = lwh
  • Volume of a Cylinder: V = Ï€r²h
  • Scale Factor Formula: Scale Factor = New Size/Original Size

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