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chapter 12
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26
Biology
Undergraduate 3
11/01/2011

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Term

law of inertia

Definition

A body will maintain a state of rest or   constant velocity unless acted   on by an external force that   changes the state. 

 

 

 

 

 

 

 

 

 

 

                                                                                                     hint - in dirt it will stay put unless dug up 

Term

law of acceleration

Definition

A force applied to a body causes    acceleration of that body

of a magnitude proportional to the   force
in the direction of the force
and inversely proportional to the   bodys mass 
f=ma                        
 
 
 
 
 
Hint: magnitude direction inversely proportinal
Accel program- MDI
 
 
 
Term

law of reaction

Definition
For every action, there is an equal   and opposite reaction.
When one body exerts a force on a   second, the second body exerts a   reaction force that is equal in   magnitude and opposite in   direction on the first body.
Term

In accordance with the law of reaction, the weight of a box sitting on a table generates a

Definition

reaction force by the table that is equal in magnitude and opposite in direction to the weight.

Term

What is friction

Definition

A force acting over the area of contact   between two surfaces

direction is opposite of motion or   motion tendency 
magnitude is the product of the   coefficient of friction (m) and the   normal reaction force (R)

   

F = mR

 

Term
static(motionless) bodies, friction is 
Definition
equal to the applied force. 
Term
For dynamic bodies (in motion), friction is 
Definition

constant and less than maximum static friction.

Term
What is momentum
Definition
quantity of motion possessed by a   body
measured as the product of a bodys   mass and its velocity;

  M = mv

Term
What is the principle of conservation of momentum
Definition

In the absence of external forces, the   total momentum of a given system   remains constant.

     M1 = M2

       (mv)1 = (mv)2

Term

What causes


momentum?

Definition

impulse: the product of a force and the   time interval over which the force   acts

  Ft

Term
What is impact
Definition

a collision characterized by:

the exchange of a large force
during a small time interval
Term
What happens following an impact?
Definition

This depends on:

the momentum present in the system
the nature of the impact
Term
What happens during impact
Definition

This is described by the coefficient of   restitution, a number that serves   as an index of elasticity for   colliding bodies; represented as   e.

Term

what does the


coefficient of


restitution (e)


describe?

Definition

  relative velocity after impact    

-e =  relative velocity before impact

  v1 - v2

-e =  u1 - u2

Term
The differences in two balls velocities before impact is 
Definition
proportional to the difference in their velocities after impact. 
Term
. The factor of proportionality is 
Definition

is the coefficient of restitution.

Term
perfectly elastic impact 
Definition
in which the   velocity of the system is conserved;   (e = 1)
Term
perfectly plastic impact 
Definition
- in which there   is a total loss of system velocity;

  (e = 0)

Term
Most impacts fall in between 
Definition
perfectly   elastic and perfectly plastic.
Term
What is mechanical work
Definition
the product of a force applied against a   resistance and the displacement of   the resistance in the direction of the   force

W = Fd

units of work are Joules (J)
Term
What is mechanical power
Definition
the rate of work production
calculated as work divided by the time   over which the work was done

    W

      P =  t

units of work are Watts (W)
Term

What is mechanical energy?

Definition
the capacity to do work
units of energy are Joules (J)
there are three forms energy:
kinetic energy
potential energy
thermal energy
Term

What is kinetic energy

Definition
energy of motion

  KE = ½mv2                                                                                   Hint- ken can move

 

 

 

 

 

 

Term

What is potential energy?

Definition
energy by virtue of a bodys position or   configuration

  PE = (wt)(ht)

Term

What is the law of conservation of mechanical energy?

Definition

When gravity is the only acting external   force, a bodys mechanical energy   remains constant.

KE + PE = C

(where C is a constant - a number that   remains unchanged)

Term

What is the principle of work and energy?

Definition

The work of a force is equal to the   change in energy that it produces in   the object acted upon.

 

W = DKE + DPE + DTE

(where TE is thermal energy)

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