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Flashcards in Equilibrium and Momentum Deck (18):
1

Equilibrium


When something is in equilibrium, the vector sum of all forces acting on it = 0.
 It moves with constant velocity.  

2

Unit for force

kg m / s2

3

Translational Equilibrium


When things are at translational equilibrium, the vector sum of all forces = 0.
 

4

Translational Equilibrium for an incline

5

Rotational Equilibrium


When things are at rotational equilibrium, the sum of all torques = 0.
 

6

Positive and Negative torques


Conventionally, positive torques act counterclockwise, negative torques act clockwise.
 

7

Newton's First Law on Equilibrium


The significance of Newton's first law on equilibrium is: things in equilibrium will remain in equilibrium unless acted on by an external force.
 

8

Newton's First Law on Momentum


The significance of Newton's first law on momentum is: things resist change in momentum because of inertia (try stopping a truck. It's not easy because it resists changes to its huge momentum).
 

9

Torque


Torque is the angular equivalent of force - it makes things rotate, have angular acceleration, change angular velocity and direction.
 

10

Lever


The lever arm consists of a lever (rigid rod) and a fulcrum (where the center of rotation occurs): F1L1 = F2L2
 





 

11

If you apply a force at a long distance from the fulcrum....

you exert a greater force on a position closer to the fulcrum

12

Real Weightlessness

when there is no net gravitational force acting on you. Either you are so far out in space that there's no objects around you for light-years away, or you are between two objects with equal gravitational forces that cancel each other out.

13

Apparant Weightlessness

this is what we "weightlessness" really means when we see astronauts orbiting in space. The astronauts are falling toward the earth due to gravitational forces (weight), but they are falling at the same rate as their shuttle, so it appears that they are "weightless" inside the shuttle.

14

Momentum


Momentum = mv, where m is mass, v is velocity and the symbol for momentum is p.
 

15

Impulse


  • Impulse = Ft, where F is force and t is the time interval that the force acts. 



  • Impulse = change in momentum
     

16

Conservation of Linear Momentum


Total momentum before = total momentum after.
 

17

Elastic Collisions 


Perfectly elastic collisions: conservation of both momentum and kinetic energy.
 

18

Inelastic Collisions


Conservation of momentum only. 

Kinetic energy is lost during an inelastic collision.