# Motion & Mechanics

Q:

## What is the law of inertia?

A:

The law of inertia states that an object at rest stays at rest and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force. The law of inertia is sometimes referred to as Newton's first law of motion.

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• #### Q:What is the Bernoulli Principle?

A: The Bernoulli Principle is the concept that claims that as the velocity of a fluid increases, its pressure decreases. Daniel Bernoulli was an 18th century scientist who discovered this principle.
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• #### Q:How do bullet trains work?

A: Bullet trains, also called maglev trains, operate with magnetic levitation technology developed by Japanese and German engineers. Japanese engineers refer to their method as electrodynamic suspension while German engineers refer to their method as electromagnetic suspension. Either way, magnets raise the trains above the track, which means there is no need for wheels.
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• #### Q:What speed breaks the sound barrier?

A: Breaking the sound barrier requires exceeding the speed of sound, which is approximately 761 miles per hour at seal level when the air temperature is 59 degrees Fahrenheit. As the temperature decreases, the speed of sound also decreases.
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• #### Q:What is an example of the application of Archimedes' principle in daily life?

A: Every time a person takes a bath, Archimedes' principle is observed as the tub is filled to a certain level and, once the bather enters the water, it rises based on the volume of water weight that the person's body displaces. Adding chicken to a pot of boiling water yields the same results but on a smaller scale.
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• #### Q:How is riding a bike an example of Newton's third law of motion?

A: Riding a bike is an example of Newton's third law of motion because the force needed to pedal a bike forward, which is the force that the tire exerts on the ground, is equal to the force of the ground pushing against the tire. The real-world example of riding a bike can also be used to demonstrate Newton's first and second laws of motion.
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• #### Q:What is simple harmonic motion?

A: In physics, simple harmonic motion refers to repetitive oscillation back and forth through a central or equilibrium position. A pendulum is a good example of a physical system that exhibits simple harmonic motion. The time taken to complete one full oscillation is called a time period.
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• #### Q:What are types of potential energy?

A: Potential energy is the stored energy of an object that has the potential to change to a different form of energy to do work. The types of potential energy are gravitational, elastic, chemical, electric and nuclear.
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• #### Q:How do water rockets work?

A: A water rocket works because of air pressure that is builds inside a container filled with water, usually a plastic soda bottle, which is released rapidly through an opening as it tries to escape. The reaction of a water rocket is an excellent example of Newton’s third law of motion, which states that forces exist in pairs.
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• #### Q:What is the difference between laminar and turbulent flow?

A: Laminar and turbulent flows are the two major forms of fluid flow, with laminar flow being an orderly flow with all the fluid molecules moving parallel in the direction of flow, whereas in turbulent flow, different streams of fluid form eddies and unpredictable currents in a different direction than the overall direction of flow. Which type of flow arises in a fluid depends on its speed relative to its viscosity and the size and shape of the pipe or other channel carrying the fluid. Viscosity is the resistance to flow, and more inherently viscous fluids are more resistant to turbulence.
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• #### Q:How do you measure the water flow through a pipe?

A: The water flow though a pipe is measured by using a mechanical flow meter. These work through positive displacement, where the volume of water flowing though in a given amount of time is measured. Domestic areas typically use a piston/rotary positive displacement meters or a nutating disk meter, while commercial areas use turbine flow meters.
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• #### Q:How do you find velocity?

A: Velocity is found by dividing the total amount of space an object moved by a measurement of time and combining that with the direction it moved. Velocity is a vector, and speed is only part of this vector.
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• #### Q:What is the meaning of "swept volume"?

A: "Swept volume" is defined as the volume of fluid through which a piston or plunger moves when it makes a stroke in an engine, according to Oxford Dictionaries. The swept volume times the number of cylinders in an engine is known as the displacement, usually measured in liters. Calculating the swept volume is done by multiplying pi times the radius squared times the height of the chamber.
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• #### Q:How does a petrol pump work?

A: A petrol pump works by using a diaphragm that pressurizes gasoline, according to Second Chance Garage. The gas transfers from the pump and through fuel line, until it reaches the carburetor.
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• #### Q:Does length affect the period of a pendulum?

A: The length of the pendulum is directly correlated to its period as per the pendulum equation: T = 2π√(L/g), where T is the period of the pendulum, L is its length, and g is the gravitational constant 9.8 m/s2. Regardless of the weight of the pendulum bob, otherwise known as the weight at the end of the string, the deciding factor of the period of the swing is length, as it is the only variable in the stated equation.
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• #### Q:Why do humans float in water?

A: Any body in water floats or sinks depending on the buoyant forces that push it up and the gravity that pulls it down. If the body is heavier than the water it displaces, it sinks. If the water the body displaces is heavier, then the body floats.
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• #### Q:What is the definition of internal force?

A: By definition, internal force is whatever causes an object with mass to accelerate or move. This force is equal to the product of the mass of the object plus its rate of acceleration.
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• #### Q:How do you calculate net force?

A: To calculate the net force, or unbalanced force, of a Newtonian object, find the sum of all forces presently acting upon it. These include gravity, friction and other forces depending on the scenario. You need only a few figures and computations to calculate an object's net force, which is required for acceleration and is expressed in Newtons.
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• #### Q:What is the law of acceleration?

A: The law of acceleration is formally referred to as Newton's Second Law of Motion and defines the rate of acceleration as a product of the force exerted on the object and the mass of the object. The rate of acceleration increases as the net force increases. The inverse is true for mass, with the acceleration decreasing as the mass increases.
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• #### Q:What are radio waves used for?

A: Radio waves are used to receive and transmit signals between two objects. These waves help to transfer signals from broadcasting stations to televisions and radios, and they are also used to transmit signals for cellular phones.
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• #### Q:What are the different types of force?

A: Forces are broadly classified into two categories: contact forces, which are required to make contact with the object in order for them to work, and action-at-a-distance forces, which can act on objects placed at a distance. Contact forces include applied force, frictional force, normal force, spring force, tension force and air resistance. Action-at-a-distance forces include gravitational force, magnetic force and electrical force.
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• #### Q:Why does wood float on water?

A: Wood generally floats because it's less dense than the water it floats on. However, some woods are denser than water and will tend to sink.
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