Vocabulary Quiz 1:
- Gravity – Force of attraction between all objects in the universe. On Earth all objects fall towards the center of Earth’s mass.
- Newton – The Newton is the basic SI unit of force.
- Weight is an example of force. An objects weight is a measure of the force of gravity acting on the object. When you weigh an object you measure the pull of gravity on the object.
- Spring scale –Measures the force of gravity on an object.
- Friction – Force that opposes the motion of an object.
- Useful Friction – makes motion possible, riding a bike.
- Harmful Friction- makes motion difficult (machine part with moving parts that touch, these parts can produce heat and can cause parts to wear out.
- Compression is the force applied when two objects are pushed together. Think of a stack of heavy stones. The force crushing down on the bottom stone is compression.
- Tension is the force applied when an object is pulled or stretched. A good example is the surface of a trampoline. When someone jumps down on the trampoline, the material stretches.
- Lubricants – materials that reduce friction such as lubricants in a car’s engine.
- Moving Against Friction – Friction makes it hard to move objects.
- Rolling Friction – reducing friction to make it easier to move objects.
- Air resistance – force that goes against (opposes) the movement of an object in air .
- Terminal velocity – speed of which air resistance and gravity acting on a falling object are equal.
- Vacuum – empty space.
- Pressure- force per unit area . Pressure = force / area
- Air pressure- pressure caused by the weight of Earth’s atmosphere.
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Energy: Vocabulary Quiz 2:
- Potential energy – the energy stored in an object because of its position.
- Thermal energy – warmth, this energy increases as its temperature increases.
- Chemical energy – the energy stored in chemical bonds. When chemicals are broken apart and new chemicals are formed, some of this energy is released.
- Radiant energy – the energy carried by light.
- Electrical energy – energy that is carried by electrical current.
- Nuclear Energy – The energy stored in the nucleus of an atom to generate electricity. Nuclear energy can be transformed into different types of energy.
- Law of conservation of energy – energy is never created or destroyed. The only thing that changes is the form in which energy appears.
- Renewable energy – this is an energy source that is replenished continually. Example – hydroelectric power plants uses rain, snow, water from rivers to generate electrical energy.
- Alternative resources- these include solar energy, wind, and geothermal energy.
- Inexhaustible resources – this is an energy source that can’t be used up by humans, such as solar energy.
- Work – work is done when a force causes an object to move in the same direction that the force is applied.
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Vocabulary Quiz 3: Loads
- Tensile strength of materials. This is the maximum force that can be applied to a material without pulling it apart.
- Dead loads — The forces applied by all of the static components of the structure, like beams, columns, rivets, concrete and dry wall.
- Live loads — The forces applied by all of the “moving” elements that can affect a structure, including people, furniture, cars, and normal weather events like rain, snow and wind.
- Dynamic loads — Dynamic loads are live loads that occur suddenly with great force. Examples are earthquakes, tornados, hurricanes and airplane crashes.
- rotational equilibrium – keeping a building “balanced.”
- One of the most important principles of structural engineering is loading.
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Newton’s Laws:
- Newton’s first law states that every object will remain at rest or in uniform motion in a straight line unless compelled to change its state by the action of an external force.
- This is normally taken as the definition of inertia. The key point here is that if there is no net force acting on an object (if all the external forces cancel each other out) then the object will maintain a constant velocity.
- If that velocity is zero, then the object remains at rest. If an external force is applied, the velocity will change because of the force.
- The second law explains how the velocity of an object changes when it is subjected to an external force. The law defines a force to be equal to change in momentum (mass times velocity) per change in time. Newton also developed the calculus of mathematics, and the “changes” expressed in the second law are most accurately defined in differential forms. (Calculus can also be used to determine the velocity and location variations experienced by an object subjected to an external force.) For an object with a constant mass m, the second law states that the force F is the product of an object’s mass and its acceleration a:
- F = m * a
- For an external applied force, the change in velocity depends on the mass of the object. A force will cause a change in velocity; and likewise, a change in velocity will generate a force. The equation works both ways.
- Thethird law states that for every action (force) in nature there is an equal and opposite reaction.
- In other words, if object A exerts a force on object B, then object B also exerts an equal force on object A.
- Notice that the forces are exerted on different objects. The third law can be used to explain the generation of lift by a wing and the production of thrust by a jet engine.