Question | Answer |
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 |