Work done on the block by force

In summary: And you need no mass, just energy and distance.In summary, a block is pushed across a rough horizontal surface from point A to point B by a force of 5.4 N. 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. The kinetic energies of the block at A and B are 4.0 J and 5.6 J, respectively. The work done on the block by the force between A and B can be calculated using the equation W = PCos (θ)D, where θ is the angle of the force.
  • #1
Zmuffinz
6
0

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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  • #2
I suppose Work done on the block = change in kinetic energy + work against friction
 
  • #3
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:
 
  • #4
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:(
 
  • #5
songoku said:
I suppose Work done on the block = change in kinetic energy + work against friction

and how do i calculate work against friction?
 
  • #6
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.
 

What is work done on the block by force?

Work done on the block by force is the energy transferred to an object, in this case a block, as a result of a force acting on it. It is measured in joules (J) and is calculated by multiplying the magnitude of the force by the displacement of the block in the direction of the force.

How is work done on the block by force related to the block's displacement?

The work done on the block by force is directly proportional to the displacement of the block. This means that the greater the displacement of the block, the more work is done on it by the force.

What is the relationship between work done on the block by force and the angle between the force and displacement?

The work done on the block by force is also influenced by the angle between the force and displacement. When the force and displacement are in the same direction, all of the force's energy is transferred to the block, resulting in the maximum work done. When the force and displacement are perpendicular, no work is done on the block.

What happens to the work done on the block by force if the force is applied at an angle?

If the force is applied at an angle, the work done on the block by force can be calculated by using the component of the force that is in the direction of the displacement. This is known as the cosine rule and takes into account the angle between the force and displacement.

Is work done on the block by force always positive?

No, work done on the block by force can be either positive or negative. If the force and displacement are in the same direction, the work done is positive. However, if the force and displacement are in opposite directions, the work done is negative as the force is working against the displacement of the block.

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