Work done on the block by force

  • Thread starter Zmuffinz
  • Start date
  • #1
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Homework Statement



A block is pushed across a rough horizontal surface from point A to point B by a force (magnitude P = 5.4 N) as shown in the figure. The magnitude of the force of friction acting on the block between A and B is 1.2 N and points A and B are 0.5 m apart. If the kinetic energies of the block at A and B are 4.0 J and 5.6 J, respectively, how much work is done on the block by the force P
between A and B?


Homework Equations


W= PCos (theta)D


The Attempt at a Solution


I have no idea what to do for this!
 

Answers and Replies

  • #2
1,767
166
I suppose Work done on the block = change in kinetic energy + work against friction
 
  • #3
tiny-tim
Science Advisor
Homework Helper
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Welcome to PF!

Hi Zmuffinz! Welcome to PF! :smile:

(have a theta: θ :wink:)
W= PCos (theta)D

I have no idea what to do for this!

Well, what is θ in this case? :smile:
 
  • #4
6
0
well you see thats why im stuck, i wasnt given an angle, or mass of the block or anything so ive got no clue as to what to do:(
 
  • #5
6
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I suppose Work done on the block = change in kinetic energy + work against friction

and how do i calculate work against friction?
 
  • #6
Doc Al
Mentor
45,180
1,502
well you see thats why im stuck, i wasnt given an angle, or mass of the block or anything so ive got no clue as to what to do:(
You didn't post the diagram, but I presume that the force was applied horizontally. That will tell you all you need about angles.
 

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