Find distance for gravity to do only -4 J of work

In summary, the student is trying to find the distance a weight will fall due to only gravity. They use the concept of work-energy to solve for the distance, but find that it is incorrect. They ask for help with a problem that is very simple, but the help they receive is not.
  • #1
P-Illiterate
28
0

Homework Statement


[PLAIN]http://img137.imageshack.us/img137/9280/43448180.jpg [Broken]
find distance for gravity to do only -4 J of work


Homework Equations


[URL]http://buphy.bu.edu/~duffy/PY105/12m.GIF[/URL]
Wg = mgX

The Attempt at a Solution


Can anyone help me from the first stepp
 
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  • #2
its urgenttt:(
 
  • #3
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  • #4
I know this is wrong because there's no way the answer can be this simple ...

W=F.d
-4 = mgsin30 * d
d = -4/20sin30
d = -.4

.4 to the left

is that even righttt?
 
  • #5
There's no force of friction?
 
  • #6
iRaid said:
There's no force of friction?

Even if there is, it won't matter since the question is asked only based on gravity.
 
  • #7
How are you getting 20sin30?

In particular, the sin30...
 
  • #8
You should use the concept of Work-Energy to solve this, since loss in energy is work.
 
  • #9
P-Illiterate said:
I know this is wrong because there's no way the answer can be this simple ...

W=F.d
-4 = mgsin30 * d
d = -4/20sin30
d = -.4

.4 to the left

is that even righttt?
To the left? Not so simple...if the work done by a force is negative, what does that imply?
 
  • #10
PhanthomJay said:
To the left? Not so simple...if the work done by a force is negative, what does that imply?

so the mass is going to the opposite direction of force ...
 
  • #11
noleguy33 said:
How are you getting 20sin30?

In particular, the sin30...
the weight component that acting on the mass
 
  • #12
can someone help meee:((
 
  • #13
P-Illiterate said:
the weight component that acting on the mass

and why are you using sin?
 
  • #14
noleguy33 said:
and why are you using sin?
the component will be sin?? should it be?
 
  • #15
Hi P-Illiterate! :smile:

(just got up :zzz: …)
P-Illiterate said:
I know this is wrong because there's no way the answer can be this simple ...

W=F.d
-4 = mgsin30 * d
d = -4/20sin30
d = -.4

.4 to the left

is that even righttt?

Yes! (assuming the 20 is correct) :smile:

except it's to the right … gravity acts down (try it! :wink:), so https://www.physicsforums.com/library.php?do=view_item&itemid=75" is positive if you go down, negative if you go up!
 
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  • #16
Thank you guys :D
I'll be back with another problem soon ... hahahah xD ^-^
 

1. How is the distance for gravity to do -4 J of work calculated?

The distance for gravity to do -4 J of work can be calculated using the formula W = mgh, where W is the work done, m is the mass, g is the acceleration due to gravity, and h is the height. By rearranging the formula, we can solve for h, which represents the distance.

2. Can the distance for gravity to do -4 J of work be negative?

No, the distance for gravity to do -4 J of work cannot be negative. Distance is a measure of how far an object has traveled, and it cannot have a negative value. However, if the work done by gravity is negative, it means that the object is moving in the opposite direction of the force of gravity.

3. Is the distance for gravity to do -4 J of work the same for all objects?

No, the distance for gravity to do -4 J of work can vary for different objects. It depends on the mass and height of the object, as well as the strength of the gravitational force acting on it. Objects with larger mass or greater height will require a greater distance for gravity to do -4 J of work.

4. What is the significance of -4 J of work done by gravity?

A negative work value indicates that the force applied and the displacement of the object are in opposite directions. This means that the object is losing energy as it moves. In the case of -4 J of work, it means that the object is losing 4 joules of energy as it moves in the opposite direction of the force of gravity.

5. How can the distance for gravity to do -4 J of work be used in real-life scenarios?

The distance for gravity to do -4 J of work can be used to calculate the potential energy of an object at a certain height. It can also be used in physics and engineering to understand the movement and behavior of objects under the influence of gravity. In practical applications, it can be used to design structures that can withstand the force of gravity and prevent objects from falling or collapsing.

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