Work done on the block by force

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Homework Help Overview

The problem involves calculating the work done on a block being pushed across a rough horizontal surface by a force, with given values for friction and kinetic energy at two points. The context is rooted in the principles of work and energy in physics.

Discussion Character

  • Exploratory, Assumption checking

Approaches and Questions Raised

  • Participants discuss the relationship between work done, change in kinetic energy, and work against friction. Some express uncertainty regarding missing information such as the angle of application and mass of the block.

Discussion Status

Participants are exploring the problem with some suggesting a relationship between work done and the change in kinetic energy, while others are questioning the lack of necessary information to proceed. There is an acknowledgment of the need for clarification regarding the angle of the applied force.

Contextual Notes

Key constraints include the absence of an angle for the applied force and the mass of the block, which are noted as significant gaps in the information provided for solving the problem.

Zmuffinz
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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!
 
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I suppose Work done on the block = change in kinetic energy + work against friction
 
Welcome to PF!

Hi Zmuffinz! Welcome to PF! :smile:

(have a theta: θ :wink:)
Zmuffinz said:
W= PCos (theta)D
…
I have no idea what to do for this!

Well, what is θ in this case? :smile:
 
well you see that's why I am stuck, i wasnt given an angle, or mass of the block or anything so I've got no clue as to what to do:(
 
songoku said:
I suppose Work done on the block = change in kinetic energy + work against friction

and how do i calculate work against friction?
 
Zmuffinz said:
well you see that's why I am stuck, i wasnt given an angle, or mass of the block or anything so I've 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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