Bensyn Science Quiz - Notes PDF

**NOTES** **Topic 1: Types of Structures** **Definition of Structures:**\ Structures are things that have a definite **shape** and **size**, which serve a definite **function** or **purpose**. To perform its function, every part of the structure must **support forces** (stresses such as pushes or...

**NOTES** **Topic 1: Types of Structures** **Definition of Structures:**\ Structures are things that have a definite **shape** and **size**, which serve a definite **function** or **purpose**. To perform its function, every part of the structure must **support forces** (stresses such as pushes or pulls) that could damage its **shape** or **stability**. **Classifying Structures** - **Natural Structures**: Occur **naturally** in the environment. - **Manufactured Structures**: Many are **modeled** after natural structures. **Design:**\ The **shape** and **size** of a structure and the **materials** of which it is composed. **Three Types of Designs:** 1. **Mass Structure** - Made by **piling**, **stacking**, or forming similar materials into a particular **shape** or **design**. - **Advantages**: Held in place by its own weight; losing small parts often has little effect on overall strength. 2. **Frame Structure** - A skeleton of strong materials, covered or filled with other materials. - **Load-Bearing Walls**: Support the weight of the structure. - **Partition Walls**: Divide spaces and do not bear loads. - Most common construction choice. 3. **Shell Structure** - Use **thin, carefully shaped outer layers** to provide strength and rigidity. - **Features:** 1. Encloses and supports. 2. Distributes forces evenly. - **Problems:** Weakness or imperfections in the covering can cause failure. **Topic 2: Describing Structures** **Areas to Consider:** 1. **Function**: What is the structure supposed to do? 2. **Aesthetics**: How it looks. 3. **Safety**: Margin of safety. 4. **Material Properties**: Characteristics must match the purpose. 5. **Construction**: How the structure is put together. **Function:**\ Examples include: - Supporting a load. - Enclosing a space. - Transporting materials or people. The **primary function** is the most important and should always be met. Most structures must meet **specific standards** that are measurable. **Aesthetics:**\ Achieved through **shape**, **texture**, **color**, **symmetry**, and **simplicity** of patterns. **Safety:**\ Structures must be **reliable** and perform as expected over time to protect people's safety and health. **Materials:** - **Properties**: Each material has unique **strengths** and **limitations**. - **Composite Materials**: Combine materials with different properties. - Example: **Layers** (e.g., plywood) glued together for combined properties. - **Woven or Knit Materials**: Interlacing fibers for added strength. **Choosing Materials:** 1. **Cost**: Can inexpensive materials perform over time? 2. **Aesthetics**: Will it remain appealing? 3. **Environmental Impact**: Does it harm the environment? 4. **Energy Efficiency**: Does it conserve energy? **Joints:** - **Mobile Joints**: Allow movement and must be lubricated. - **Rigid Joints**: Examples include fasteners, ties, interlocking shapes, adhesives, and melted joints. - **Fasteners**: Nails, staples, bolts, screws, rivets, and dowels. - **Interlocking Shapes**: Fit together due to their shape. - **Adhesives**: Can fail under extreme conditions. - **Melting**: Welding and soldering fuse materials together. **Topic 3: Mass and Forces** **Mass:**\ Mass is the number of particles in a substance. Measured in **kilograms (kg)** or **grams (g)**. **Balance:**\ A **balance** compares the mass of an object to a known standard. **Forces and Weight:** - **Force Unit**: Newton (N). - **Force Meter**: Measures the pull of gravity on a mass. **Weight:** - The gravitational force between two objects depends on their masses and the distance between them. - **Mass** is the amount of matter in an object. - **Weight** is the gravitational force on an object. **Topic 4: Forces, Loads, and Stresses** **External Forces:** - **Static Load**: Permanent force acting on a structure. - **Dynamic Load**: Changing, non-permanent force. - **Impact Forces**: Collisions with the structure. **Internal Forces:** - **Tension**: Pulling apart. - **Compression**: Pushing together. - **Shear**: Sliding forces. - **Torsion**: Twisting forces. - **Bending**: Combination of tension and compression. **Resisting Stress:**\ Material strength depends on particle attraction and direction of forces. Examples: - Steel: **Strong particle attraction**. - Graphite: **Weak particle bonds**. - Rubber: **Flexible bonds**. **Topic 5: How Structures Fail** **Material Failures:** - **Shear**: Particles separate, causing cracks. - **Bend/Buckle**: Compression causes deformation. - **Torsion**: Twisting damages structure integrity. - **Metal Fatigue**: Repeated stress causes cracks. **Preventative Reinforcements:** - Add **triangles** or **cross-bracing** for strength. - Use **I-beams**, **L-beams**, or **corrugated shapes**. **Topic 6: Designing with Forces** **Key Methods:** 1. **Distribute the Load**: Spread forces across the structure. 2. **Direct Forces**: Control the path of forces. 3. **Shape Strength**: Design to withstand forces. **Structural Problems and Solutions:** - **Braces**: Add strength by forming rigid triangles. - **Cantilever**: Horizontal supports anchored at one end. - **Arches**: Use a central keystone for strength. - **Beams**: Use cylindrical or hollow beams for efficiency. **Using Friction:**\ Friction helps stabilize structures and resist sliding. **Topic 7: Stable Structures** **Stability Factors:** - Balance forces to prevent collapse. - Locate **center of gravity** to ensure stability. - If the center of gravity shifts outside the base, the structure becomes unstable. **Firm Foundations:** - Built on **stable ground** or solid bedrock. - Use **pilings** or **packed layers** to distribute the load. - Spread load over a larger area. **Spin Stabilization:**\ Rotational speed can improve stability for some structures (e.g., satellites). **TEST REVIEW** **Topic 1: Types of Structures** **Definition of Structures:** Structures are things that have a definite **shape** and **size**, which serve a definite **function** or **purpose**. To perform its function, every part of the structure must **support forces** (stresses such as pushes or pulls) that could damage its **shape** or **stability**. **Classifying Structures** - **Natural Structures**: Occur **naturally** in the environment. - **Manufactured Structures**: Many are **modeled** after natural structures. **Design:** The **shape** and **size** of a structure and the **materials** of which it is composed. **Three Types of Designs:** 1. **Mass Structure** - Made by **piling**, **stacking**, or forming similar materials into a particular **shape** or **design**. - **Advantages**: Held in place by its own weight; losing small parts often has little effect on overall strength. 2. **Frame Structure** - Have a skeleton of strong materials filled or covered with other materials. - **Load-Bearing Walls**: Support the structure. - **Partition Walls**: Divide spaces. 3. **Shell Structure** - Structures that **enclose** and **protect** without a frame or solid mass inside. - Use a thin, shaped outer layer for strength. - **Advantages**: Spread forces throughout the structure for strength. - **Disadvantages**: Tiny weaknesses can cause failure. **Topic 2: Describing Structures** **Areas to Consider:** 1. **Function**: What the structure is supposed to do. 2. **Aesthetics**: How it looks (shape, texture, color, symmetry). 3. **Safety**: Margin of safety to ensure reliability. 4. **Materials**: Must match the structure\'s purpose. 5. **Construction**: How the structure is fastened or put together. **Margin of Safety:** Structures must be built to perform as expected for a long time, keeping people safe. **Types of Joints:** - **Mobile Joints**: Allow movement (e.g., hinges, lubricated joints). - **Rigid Joints**: Fixed connections (e.g., fasteners, ties, adhesives, welding). **Topic 3: Mass and Weight** **Mass:** The amount of matter in an object (measured in kilograms, kg). **Weight:** The force of gravity acting on an object\'s mass (measured in newtons, N). **Difference:** - Mass is constant and does not change with location. - Weight depends on gravity and changes with location. **Topic 4: Forces, Loads, and Stresses** **External Forces:** 1. **Dead Load**: Permanent forces acting on a structure. 2. **Live Load**: Non-permanent forces that change. 3. **Impact Force**: Forces from collisions. **Internal Forces:** 1. **Tension**: Pulling force. 2. **Compression**: Pushing force. 3. **Torsion**: Twisting force. 4. **Shear**: Sliding force. 5. **Bending**: Combination of tension and compression. **Resisting Stress:** - **Tensile Strength**: Resistance to tension. - **Compressive Strength**: Resistance to compression. - **Shear Strength**: Resistance to shear forces. **Topic 5: How Structures Fail** **Material Failure:** - **Shear Failure**: Particles slide apart. - **Bending/Buckling**: Compression causes deformation. - **Torsion Failure**: Twisting causes breaking or loss of shape. - **Metal Fatigue**: Repeated stress causes cracks over time. **Making Use of Stress:** - Reinforcements like braces or trusses can strengthen structures. **Topic 6: Designing with Forces** **Three Key Methods:** 1. **Distribute the Load**: Spread forces evenly. 2. **Direct Forces Along Angled Components**: Use shapes like triangles. 3. **Shape Parts to Withstand Forces**: Design materials to handle specific stresses. **Structural Problems and Solutions:** - **Problem 1:** Frame structures can be pushed or pulled out of shape. - **Solution:** Use braces to form rigid triangles. - **Problem 2:** Horizontal forces can cause bending. - **Solution:** Use cylindrical or I-beam shapes. - **Problem 3:** Weak foundations lead to instability. - **Solution:** Use solid layers or pilings. **Using Frictional Forces:** Friction helps hold structures in place, especially against wind or other external forces. **Topic 7: Stable Structures** **5 Principles of Stability:** 1. **Center of Gravity**: Balance the structure around a central point. 2. **Thrust Line**: Ensure forces stay within the base of the structure. 3. **Symmetry**: Evenly distribute mass. 4. **Firm Foundation**: Build on stable ground. 5. **Balanced Forces**: Counteract external forces for stability. **Rapid Rotation:** Spinning objects maintain stability through centripetal forces.