# College Physics Ch. 7 Notes

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Centripetal (term)

-Quantity that always points towards the center of the circle —–\”Center Seeking\” -Originated by Newton
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Centripetal Acceleration

-acceleration pointed towards the center of the circle -keeps object moving in a circular path
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Period

-time needed to complete one revolution —Ex. rpm
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Velocity (Tangential Velocity)

-perpendicular to the radius and acceleration —object’s velocity pointed in a direction tangent to the circle
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Centripetal Force

-force that causes the acceleration towards the center of the circle
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What forces are constant in a Horizontal circle?

Fc Vt ac
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What forces are constant in a Vertical circle?

none?
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Critical Velocity

-Vmin -the minimum velocity needed to continue the circular path ***TENSION=0 N***
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Centrifugal Force

-imaginary force a person feels traveling on an object traveling in a circle ***NO FORCE, just an object traveling in a straight line*** EX: —passenger in a car on a curve —roller coaster rider
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Gravitational Force

***Orbiting objects are in free fall*** -The centripetal force that holds the planets in orbit is the same force that pulls an apple toward the ground
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What is the constant G?

-Constant of Universal Gravitation ***6.673×10^-11***
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Gravitational Forces are..?

-equal in magnitude and opposite in direction -an example of Newton’s third law of motion
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Earth-moon system

-accounts for ocean tides -high and low tides are partly due to the gravitational force exerted on Earth by its moon.
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What kind of force is gravity?

Field force
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Gravitational field strength is also known as..?

Free-fall acceleration
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Because it depends on gravitational field strength, weight changes with..?

Location
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On the surface of any planet, the value of g will depend on the planets..?

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Lever arm (d) Torque arm (m)

The perpendicular distance from the axis of rotation to a line along which the force acts.
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Torque (t)

The product of the force and the lever arm. (Nm) (Kgm^2/s^2)
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Center of Gravity (com)

Point at which all the mass of body can be considered concentrated. Balance point. In uniform objects it is in the middle.
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Parallel Forces

Forces that act on different points in an object in the same place.
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Translational Equilibrium

When upward forces equal downward forces.
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Rotational Equilibrium

Condition when the clockwise torque equals counterclockwise torque.
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Moment of Inertia