Gr 7 Unit D Test (Section 3-4)
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What is deformation?
The change in size or shape of an object
What is flexibility?
The ability of a material to be bent under force but not break. It helps prevent a structure from deforming and breaking
What are qualitative observations?
Qualitative observations deal with data that can be observed but not measured. (no numbers)
What are quantitative observations?
Quantitative observations deal with quantities and numbers
What are the properties of a material?
Brittleness, ductility, hardness, plasticity, resistance to heat/water, compression, and tensile strength
What is ductility?
Ductility describes the property of a solid material and how thin it can be stretched when in tension. If a material is ductile, it could be stretched into a wire
What is hardness?
How hard something is
What is plasticity?
The property of how easily something can be easily shaped or molded
What is resistance to heat/water?
How much an object can resist heat flow and penetration by water
What is compression (as a property)?
How well an object can deal with compression
What is tensile strength?
Tensile strength is a measurement of the force required to pull something to the point where it breaks
What is brittleness?
Brittleness describes the property of a material that when stressed, fractures without deforming first
What are joints?
Joints are structures that connect 2 structures together
What are fixed joints?
Joints that are rigid and don’t move
What are moveable joints?
Joints that can move
What is friction?
Force caused when surfaces of 2 objects rub against each other
What are some joints that rely on friction?
• Nails screw, rivets, tacks, and staples (friction between the metal and the material surrounding it that does the job) • Interlocking pieces (increase area of contact->increases friction) • Mass (bricks)
What are some joints that rely on bonding?
• Glue, tape, cement, welds (surfaces harden together into 1 solid mass)
What are some materials in the human structure? (I don’t think we need to know these but just in case here they are)
Bones - hard and rigid Cartilage - reduces friction, provides a smooth surface for movement and absorbs shock Ligaments - bands of strong connective tissue that can join bones together Tendons - strong and flexible tissue that attaches muscle to bones Muscles - fibrous tissue that allow bones to move by contracting and relaxing
What are the different joints in the human body? (might not need to know but still)
Ball and socket - hips and shoulders Hinge - elbows and knees Pivot - spinal column (it twists) Gliding - wrists
What does the skin do in the human structure? (another might not need to know but still)
Provides structural shelter by waterproofing the body and protects it from bacteria. Skin also regulates body temperature.
_______, _______, and _______ rely on the proper use of materials
Stability, strength and function rely on the proper use of materials
What is a margin of safety?
The limits within a structure’s safety performance is considered to be acceptable (speed limits, weight limits, etc)
How can the margin of safety be found out?
• Through safety testing - using greater than normal forces to see when it fails • Through people looking to see how often the structure fails and why