Term
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Definition
Force- act necessary to produce linear motion
Torque- the act necessary to produce angular motion (or to make an object twist, spin, or rotate) |
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Term
| State the two conditons of equilibrium |
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Definition
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Term
| Discuss the physics of circular motion |
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Definition
| To produce circular motion, an object must be moving at a constant speed on a horizontal surface. It is accelerating because of the change in direction. Also, there must be a net force acting on the object for it to accelerate, and any force can produce circular motion. The acceleration and Fnet are always towards the center of the circle, and there must always be a force to keep the object in circular motion. |
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Term
| Discuss centripetal and centrifugal forces, including frames of reference |
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Definition
Centripetal is a force acting towards the center of the circle
Centrifugal is a false force, which acts away from the center of the circle
Frames of reference are a set of axes which the position or motion of an object can be described
Equilibrium exists in the rotating frame if all forces balance, including an inertial "centrifugal" force |
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Term
| What must occur for an object to tip over? |
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Definition
| The objects center of mass must stay inside the axis of rotation |
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Term
| Why won't a sphere tip over? |
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Definition
| The center of mass of a sphere is located at its center, and it is always supported at its center when balancing. Its axis of rotation is also at its center, so its center of mass cannot go outside of the axis of rotation |
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Term
| What will a net torque do to an object? Net force? |
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Definition
An object will stay in rotation unless acted upon by an external net torque.
If there is a net force acting on a mass, then it must be accelerating. |
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Term
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Definition
| the point at which the entire mass of a body may be considered concentrated |
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Term
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Definition
| Lever arm (distance from the axis of rotation to the applied force) and Force |
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Term
| If torque is constant, how are the other two quantities related? |
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Definition
| F α1/r; inversely proportional |
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Term
| Why does a mechanic put a pipe extension on a stubborn nut? |
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Definition
| To increase the lever arm; τ α r, so increasing the lever arm increases the torque and the nut will come off. |
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Term
| At maximum torque, how are the two quantities related? |
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Definition
| F is perpendicular to r (torque is at a maximum at 90° |
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Term
| Why is it difficult to open a jar with wet, soapy hands? |
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Definition
| If friction is one the force acting to produce the circular motion to open a jar, then wet, soapy hands decreases the coefficient of friction, making it more difficult to open. |
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Term
| Discuss the physics of a rock being whirled at the end of a string at constant speed. |
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Definition
| UCM, the acceleration and force act towards the center of the circle. There is always a force keeping the rock in circular motion, once this force stops acting on the rock, it will accelerate linerally. |
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Term
| State and discuss Kepler's laws of planetary motion. |
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Definition
I. Orbit of the planets are elleptical with the sun.
II. Equal areas in equal times (the closer a planet is to the sun, the faster its moving)
III. The square of a planet's orbital period (T^2) is proportional to its avg distance to the sun cubed (r^3) [T^2 α r^3]
Used experiments to discover the laws of nature |
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Term
| State and discuss Hooke's Law. |
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Definition
F=kΔx
Force is proportional to displacement |
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Term
| Who is Tycho Brahe? What did he contribute to astronomy? |
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Definition
well known astronomer who was assisted by Kepler. When he died, Kepler used his astronomical results to develop his own theories of astronomy.
He observed the planetary motion particularly of mars, and obtained crucial data that Kepler later used. |
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Term
| What forces can produce circular motion? |
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Definition
Any force:
-normal
-tension
-friction
-gravitational
-centripetal v centrifugal |
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Term
| Why does jupiter have a period longer than 1 year? |
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Definition
| Earth is 1 AU from the sun, and a period is one year. Jupiter is almost 5 AU from the sun, so the period is much longer. |
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Term
| Where is the earth moving faster around the sun, January or July? |
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Definition
| January, because it is closer to the sun. Kepler's second law, equal areas equal times, says that when a planet is closer to the sun it is moving faster. |
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Term
| How does a tight rope walker stay on the wire? |
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Definition
| Balancing center of gravity, keeping their center of mass withing their axis of rotation |
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Term
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Definition
| V=Vo-at; how fast an object accelerates linearly |
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Term
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Definition
| ω=ωo-αt; how fast an object is rotating (accelerating angularly) |
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Term
| convert 10rev/min to rad/sec |
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Definition
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Term
| How are v and ω related mathematically? |
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Definition
| v=Rω; v is proportional to ω |
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Term
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Definition
I is the moment of intertia (resistance to an objects change in angular velocity)
This equation means that an object will stay in rotation unless acted upon by an external net torque. |
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Term
| Define I, moment of inertia |
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Definition
| Resistance to an objects change in angular velocity |
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Term
| Write Newton's laws using τnet |
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Definition
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Term
| Define geosynchronous orbit. How far from earth's surface is a satellite in geosynchronous orbit? |
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Definition
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Term
| Can a yo-yo be whirled fast enough to be completely horizontal? |
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Definition
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Term
| Use the gravitational force to determine g as a function of distance from the center of earth. Is g constant? |
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Definition
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