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# THE MCAT-PHYSICS 2

### FORCES

The force of air resistance is ALWAYS constant for any mass. T/F TRUE
What changes force of air resistance? speed, SA, shape
What does mass change with AR then? changes effect of air resistance (path) but doesn't change air resistance F=ma and bowling pins
Why does a large mass and small mass fall at the same rate? Larger inertia associated with larger mass means a larger force required to change its motion at the same rate
Universal gravitation: What do two objects experience? Experience same gravitational force but acceleration is different
What is weight? measure of gravitational force on a body
rotational inertia? measure of an object's resistance to changes to its rotation
What is center of mass? single point where a single force can be applied in any direction causing all points in system to accelerate equally
Inclined plane: When frictionless, what forces act? gravity and normal force
What do machines do? reduce amount of force needed to accomplish a task
What don't machines do? reduce amount of work that needs to be done
Mechanical advantage equation? weight of object to be supported / applied force needed to support object
What do you need to overcome when push object up inclined plane? Overcome both parallel component of gravity and friction
Inclined plane: nonmoving object parallel vector of gravity = static friction
Inclined plane: object going down @ constant velocity parallel vector of gravity = kinetic friction
Inclined plane: object accelerating down inclined plane parallel vector of gravity > Fk
Inclined plane: object begins to slip on inclined plane parallel vector of gravity > Fs
What are the forces acting on a block on inclined plane? gravity and normal force
centripetal acceleration -speed never changes but object is always accelerating -points toward center of circle
centripetal force -points toward center of circle -acceleration is ALWAYS accompanied by a force -Fc is created by gravitational force
What are the ONLY 3 forces? -gravitational, electromagnetic, contact -these forces create and cause all other forces
Stuff moving in a circle? Think --> F = mv^2 / r
Kepler's Laws 1.) All orbital paths elliptical 2.) orbiting object moves faster and subject to greater force when closer to object it orbits 3.) T^2 is proportional to R^3
What is apparent weight often associated with? normal force
Elevator accelerating up = Elevator decelerating down = -elevator decelerating down -elevator decelerating up
what forces act on uniform circular motion? centripetal force (centripetal "a" ) directed towards center of circle
What forces act on nonuniform circular motion? tangential force to change "a" and centripetal force produce resultant force and "a" NOT directed towards center of circle
Contact situations always have what forces? Fn perpendicular and frictional parallel
Is static friction constant? NO --> can reach a threshold point
Is kinetic friction constant? Yes! once it moves it moves
Which is greater, u(s) or u(k) friction? u(s)
Can static friction accelerate an object from rest? YES
What does frictional force oppose? -applied force -no applied force - frictional force does all of the work
Why (-) in Hooke's Law? force is opposite direction to displacement
translational equilibrium constant speed (0 or nonzero) and constant direction
rotational equilibrium not rotating or constant rotation
static equilibrium velocity is constant 0
dynamic equilibrium velocity is constant and not zero
What does a non-equilibrium state mean? There is acceleration!
How to change angular velocity? Apply torque
What are some examples of external forces? friction, air resistance, normal, applied force
How does external force affect total ME? -External forces are nonconservative forces -change the total ME depending on whether positive or negative work
What are examples of internal forces? gravity, magnetic, electrical, spring force
How does internal forces affect total ME? -Internal forces are conservative forces -do not change the total ME -type of energy form changes
What is work done for external forces equal to? change in mechanical energy
Is work the same as energy? NO --> work is when a quantity of energy is moved from one system to another
What remains constant for conservative forces? sum of kinetic and potential energies
Law of Universal Gravitation Equation F = Gm1m2 / r^2
Kinetic Friction equation Fk = uk * Fn
Static Friction equation Fs = us * Fn
What is static friction? friction opposing motion when a stationary object and surface are not moving
What is kinetic friction? force resisting motion once stationary object and surface are moving
When is coeff of friction max? when 2 surfaces are not moving
Once a block starts to slide, is there acceleration? YES
Mutual forces exerted during collisions are equal / unequal in magnitude? equal
What does friction depend on? coefficient of friction, angle, and normal force
As angle increases for a box on an inclined plane, ____ decreases which causes net accelerating force acting on box. normal force
As soon as equilibrium is disrupted, there is _____. acceleration
What happens to the peak height when you kick an object into air with air resistance? reaches lower peak, takes longer to reach ground than peak
What does backspin create and what to do to compensate? additional flight time --> decrease launch angle
What does topspin create and what to do to compensate? reduces flight time --> increase launch angle
Can friction cause acceleration? YES
Does friction do work on an object? YES --> drains energy
Considering air resistance, why does an elephant fall faster than a feather? -elephant never reaches terminal velocity --> accelerates constantly -feather quickly reaches terminal velocity
Considering no air resistance, does an elephant or feather fall faster? fall the same
Does the force of AR ever change for a mass? NO
What does AR take away from an object? takes away energy
Why does large SA increase AR? more collisions with air molecules
HIgher the velocity, higher /lower AR? greater the AR
Why do larger masses experience less deceleration due to AR? F= m*a -force constant, mass increases, a decreases
In a collision, two objects hit each other with? equal force
Does mass change if gravity changes between two planets? NO --> only weight changes
With an elevator, is the tension of the cable line ever zero? NO
Moving in from a larger circle to a smaller circle, does tangential speed increase or decrease? decrease
2 important rotational motion equations? -a = v^2 / r (tangential speed) -w = v/r (angular velocity)
Does a planet's orbit depends on the planet's mass? NO
Does an orbiting object move faster or slower when orbital radius decreases? faster
Higher coefficient of friction means? greater friction
Can static friction accelerate object from rest? YES
Why is it harder to start walking on an icy floor than a carpeted floor? us for ice is much lower than us for carpet
Is acceleration on an inclined plane parallel / perpendicular to surface of plane? PARALLEL
Mechanical advantage weight of object to be supported / actual applied force to support object
What is the mechanical advantage of an inclined plane? 1 / sin theta
How does the tension change within a rope in a pulley system? IT DOESN'T CHANGE --> CONSTANT THROUGHOUT
Created by: 507935299

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