August friction

Document Sample
August friction Powered By Docstoc
					October 21
    physics
In:
 What do
    you think
    affects
    the force
    of
    friction?
Objective:

 To  build an understanding
  of the force of friction.
Success criteria:
 Understand the variables
  that make up friction.
Discovery Lab:
Force of friction
    List the possible variables that make up
     the force of friction
    Using the force probe and friction block,
     test each variable.
    Data:
    1. Variable 1:
       a)   How are you testing it
       b)   What was your result
    2. Variable 2 :
    ….Etc…
What did we find out:
Force of friction

   Static Force of Friction
    – Force needed to start an object moving
   Kinetic Force of Friction
    – Force needed to keep an object moving
Ff=µFn

Force of static friction uses µstatic
  – The force it takes to get something
    moving
Force of kinetic friction uses µkinetic
  – The force it takes to keep it going at a
    constant velocity
Mass=32 kg
µs = .7
µk = .3
Find the force to get
  the box moving.
Find the force to keep
  the box moving at a
  constant velocity.
A 700 kg polar bear
  slides across the ice
  with a force of friction
  of 25 N.
What is the coefficient
  of friction between
  fur and ice?
A 25 kg boy slides
  along a slip-n-slide.
  He slows down with
  an acceleration of .5
  m/s2. What is µk
  between the slide and
  the boy?
A group of people pull a 200,000 kg
  plane with a force of 40,000 N to keep
  it moving at a constant velocity.
 What is the kinetic force of friction?
 What is the coefficient of kinetic
  friction of the tires on the tarmack?
Out:

   Draw a free body diagram of your
    friction block in constant velocity.

				
DOCUMENT INFO
Shared By:
Categories:
Stats:
views:3
posted:3/24/2011
language:English
pages:16