Mechanics Flashcards
Uniform accelerated motion
Velocity is changing. Acceleration is constant
For projectile motion, if acceleration is zero throughout flight, what is horizontal velocity?
Constant
Newton’s second law
Force equals mass times acceleration
Newton’s first law
Force must be applied for an object to move
Newton’s third law
For every action there is an equal but opposite reaction
If there is no force but object is moving, velocity must be
Constant
If masses are different will the action reaction be the same?
No
What kind of friction is rolling resistance?
Static friction
True or false action reaction pairs work on same objects
False
Kinetic friction is always what to velocity?
Parallel and opposite
True or false coefficient of static friction is always greater than coefficient of kinetic friction
True
For an inclined plane what is the force due to gravity?
Mg sin theta
What do pulleys change the direction of?
Tension
What is the center of mass?
Point where object acts as a single particle
What is center of gravity?
Point where total gravitational force on the system can be considered to act
What is uniform circular motion?
Object moving in a circular path with its speed held constant
Why is velocity not constant in uniform circular motion?
Direction is constantly changing
In uniform circular motion, velocity is always what to its path?
Tangent
In UCM, where does acceleration point?
Center of circle. Velocity and acceleration are always perpendicular to each other
What provides centripetal force?
Gravity and tension force
What is centripetal force?
Net force directed toward the center
What dies tangential acceleration change?
Speed making the object not in UCM
In tangential acceleration, where does speed start to decrease?
As it rises to the top of the circle and opposed to the velocity vector
What is torque?
Measure of force to make an object spin or rotate
What is the fulcrum?
The center of turning
If there is no torque, what cannot be decreased?
Rotational speed
When is max torque reached?
When the angle equals 90 degrees
For torque, clockwise is
Positive
For torque counterclockwise is
Negative
If the force acts at the pivot, what is the torque?
Zero
What is the lever arm perpendicular to in torque?
Line of action of force
What is work equal to?
Work equals distance times force, when force and distance are in the same direction
What is the unit for work?
Joule
What kind of forces always do zero work?
Perpendicular
When is W= Fdcos used?
Force is constant
What is power?
Measures how fast work gets done
What is the unit for power?
Watt (Joules/sec)
How much is one horsepower?
750 watts
What is gravitational potential energy?
Moving a object higher or lower. It is opposite of work done by gravity
Work done by gravity depends mainly on
Height
If there is less effort force, what must be covered to satisfy work requirements?
Larger distance
What is mechanical advantage?
Resistance force over effort force. Use the factor to find amount of force required without the machine
What is resistance force?
Force applied if no machine were being used
What is efficiency?
Degree to which friction and other factors reduce actual work output of machine from its theoretical max
What is the equation for efficiency?
Work output/ energy output
What can you use efficiency for?
Figuring out what % of energy is being lost
What is impulse?
Force X time
Momentum changes are
Equal but opposite
What is equation for linear momentum?
P= my
Is KE conserved in an elastic collision?
Yes
Is KE conserved in an inelastic collision?
No
What is a perfectly inelastic collision?
When objects stick together after colliding
What does inelastic collisions result in?
Max possible loss of KE
What is the rate of change for angular momentum?
Torque
What is rate of change for linear momentum?
Force
