# Shared Flashcard Set

## Details

Circular Motion & Universal Gravitation
Concepts and Formulas
41
Physics
10/10/2012

Term
 Uniform Circulation Motion def
Definition
 motion in a circle of a constant radius at a constant speed
Term
 In uniform circular motion, instaneous velocity is always ____ to the circle
Definition
 tangent
Term
 give  the formula for the acclertaion in  uniform circular motion
Definition
 aR= v2     r unit: m/s2
Term
 For an object to be in uniform circulation there must be ______
Definition
 a net force acting on it   ex. like swinging a ball on a string
Term
 The accleration in uniform circular motion is called____ or ____ accleration and it points__________ of the circle
Definition
 centripetal or radial accleration, towards center
Term
 If the centrigufal force vanishes  the object will fly ____ to the circle instead of _____
Definition
 off tangent, outward   the natural tendency of the object to  move in a circle must be overcome
Term
 express the acceleration in uniform circualr motion in terms of force
Definition
 ΣFR= maR= m v2                       r   recall that sum of net force= accleration x mass
Term
 Describe how a car travels along a curve, what forces are acting? If the roads is flat?
Definition
 there must be a net force towards the center of the actual curve (which is arc shaped ∩)   b. If the road is flat the force is friction
Term
 Highway Curves, Banked & Unbanked: If the frictional force is insufficent the car will tend to move in a ____
Definition
 straight line
Term
 The Clothoid Loop The radius at the bottom is significantly (smaller/bigger) than the radius at the top of the clothoid loop
Definition
 bigger
Term
 Highway Curves, Banked, and Unbanked ___________ the curve can help cars from skidding
Definition
 banking
Term
 Describe how banked highway curves  works.
Definition
 There is ONE speed in which the : entire centripetal force is supplied by the HORIZONTAL (x)component of the NORMAL force NO friction is required!
Term
 Give the formulas that make banking of highway curves possible.
Definition
 (x) FN cos Ө = mg              (y) FN sin Ө =mac =  (mg   )   sin Ө                              (cosӨ)   = (m’s will cancel) = (g/cosӨ) sin Ө = v2 /r (recall sin/cos = tan)   = g tan Ө = v2 /r Final Equation: V=√gr tan Ө
Term
 Newton's Law of Universal Gravitation If the force of gravity is being excerted on objects on Earth, what is the origin of the force?
Definition
 this force comes from the Earth, this force also keeps the Moon in its orbit.
Term
 What 2 factors influence the gravitional force & why?
Definition
 the gravitional force is proportional to both masses involved  (aka the Earth excerts a  downward force on you & you excert an upward force on Earth b/c these masses are very opposite the rxn is small & negliable , however the rxn force btwn the Earth & moon is SIGNIFICANT) the gravitional force  decreases as the distance btwn the two masses increases (distance is measured from the center of both of the masses being considered) (which can be represented by radius squared)
Term
 Write the formula for Law of Universal Gravitation
Definition
 F= G m1m2 r2 where G=6.67 x 10-11 N•m/kg2 r= distance btwn objects m1= object/planet staying still m2= one that is moving
Term
 The mass of the Earth is
Definition
 5.98 x 1024 kg
Term
 Satellites & Weightlessness   How do satellites work?
Definition
 the tangential speed: must be HIGH enough so that satellite does not return to Earth but not too high that it escapes Earth's gravitional pull
Term
 The satellite is kept in orbit by its ____
Definition
 speed, it is continually falling, but the Earth curvees from Earth underneath it.
Term
 T or F: Objects in orbit do not have a gravitional force acting on them.
Definition
 False, alhough objects in orbit are said to experience a gravitational force,there is still a gravitional force. The satellite & all of its components are in FREE FALL= no normal force (thats where the feeling of weightlessness comes from)
Term
 What is apparent weightlessness
Definition
 Just like the:  satellite & all of its components are in FREE FALL= no normal force (thats where the feeling of weightlessness comes from)
Term
 Keplers Laws describe
Definition
 planetary motion
Term
 Keplers First Law: The orbit of each is
Definition
 an ellipse, with the sun at one focus
Term
 Kepler's 2nd Law: an imaginary line____...
Definition
 drawn from each planet to the Sun sweeps out equal areas in equal times.
Term
 Kepler's 3rd  Law: relate the orbit & orbital law
Definition
 the period2  of the orbit for all objects orbiting the same planet/star depends on orbital distance3
Term
 Give formula for Kepler's 3rd law that relates M, r,G, T2
Definition
 (4∏2/GM)• r3 = T2   where T2 = the period squared for all objects orbiting the same planet/star G= 6.67 x 10-11 r3 = orbital distance cubed M= mass of planet staying still *note :memorze this formula b/c it can switched around to solve for other variables for example if you want to find the mass of a planet knowing how far it is from Earth
Term
 The greater the speed v, then ____ & The greater the radius then______
Definition
 the higher the speed: the FASTER the velocity changes direction   the higher the radius: the LESS rapidly the velocity changes direction
Term
 frequency give letter
Definition
 f
Term
 frequency,f, def
Definition
 # of revolutions per second
Term
 period is represented by what letter?
Definition
 T
Term
 period,T, def
Definition
 time required for 1 complete revolution
Term
 Give the equation that relates period + frequency
Definition
 T=1      f
Term
 Give the equation for an object revolving in a circle (of circumference 2πr), at a constant speed v
Definition
 v= 2πr T This is true because when an object travels 1 circumference it also traveled one revolution.
Term
 newtons gravitational force formula: F=G m1m2/r2 unit for distance
Definition
 m
Term
 newtons gravitational force formula: F=G m1m2/r2 unit for mass
Definition
 kg
Term
 newtons gravitational force formula: F=G m1m2/r2 unit for answer
Definition
 N
Term
 Give formula for Kepler's 3rd law that relates the period (T) and the orbital radius (r) for two planets
Definition
 (T1/T2 )2 = (r1 / r2 )3 * use this formula when you want to determine the distance of planet (r) from anothe planet, knowing its period (T).
Term