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

  • Thread starter Thread starter P-Illiterate
  • Start date Start date
  • Tags Tags
    Gravity Work
Click For Summary

Homework Help Overview

The discussion revolves around calculating the distance over which gravity does -4 J of work. The context involves concepts from mechanics, specifically work done by gravitational force.

Discussion Character

  • Exploratory, Assumption checking, Conceptual clarification

Approaches and Questions Raised

  • Participants explore the relationship between work, force, and distance, questioning the application of the work-energy principle. There are attempts to derive the distance using the equation W = F.d, with specific reference to gravitational force components.

Discussion Status

Multiple interpretations of the problem are being explored, particularly regarding the direction of the force and the implications of negative work. Some participants express uncertainty about their calculations and the assumptions made regarding the force components involved.

Contextual Notes

There is a mention of the absence of friction and the focus solely on gravitational work. Participants also discuss the relevance of angle components in the force calculations.

P-Illiterate
Messages
28
Reaction score
0

Homework Statement


[PLAIN]http://img137.imageshack.us/img137/9280/43448180.jpg
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
 
Last edited by a moderator:
Physics news on Phys.org
its urgenttt:(
 
Last edited by a moderator:
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?
 
There's no force of friction?
 
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.
 
How are you getting 20sin30?

In particular, the sin30...
 
You should use the concept of Work-Energy to solve this, since loss in energy is work.
 
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!
 
Last edited by a moderator:
  • #16
Thank you guys :D
I'll be back with another problem soon ... hahahah xD ^-^
 

Similar threads

  • · Replies 3 ·
Replies
3
Views
3K
  • · Replies 1 ·
Replies
1
Views
5K
  • · Replies 1 ·
Replies
1
Views
1K
Replies
2
Views
3K
  • · Replies 6 ·
Replies
6
Views
2K
  • · Replies 4 ·
Replies
4
Views
2K
  • · Replies 5 ·
Replies
5
Views
4K
Replies
11
Views
8K
  • · Replies 1 ·
Replies
1
Views
5K
  • · Replies 5 ·
Replies
5
Views
4K