Weird science question - force vs force

[LordRaiden]

Ok, I admit it. I'm a science nut. But this one has me sort of baffled. Here's the question.

How is the following rule true: "It takes an equal amount of force to apply an object as it does to remove it."

The examples given were a screw, a nail, a door, a car, and nut. The answers were as follows.

1. This rule is absolute.
2. This rule is relative.
3. This rule is false.

What do you think? I would believe it would be relative to the situation. But at the same time the rule could also be absolute and false at the same time depending on the situation.

 

[white]

isn't force a vector?

 

[Heisenberg]

It would be dependent on the situation. Basically it has to with if you're dealing with conservative forces or not.

Edit: And it should probably say 'work' or 'power' in the question, not 'force'.

 

[raptor13]

If it's absolute sometimes and false at other times, that makes it relative, does it not?




As for the examples, a nut would take as much energy to apply as to remove in almost all cases, but think about a screw. When you first screw it in, say into a piece of wood, you have to displace wood to make room for the screw and overcome the friction between the screw and the wood. When you're taking the screw out, the only thing preventing you from doing so is friction. You longer have to displace material so removal is easier. Thus, in this case, the "rule" is false. The nut case is true. Hence, the rule is relative.



EDIT: They've made a good point about conservative and non-conservative forces. Are these situations supposed to be ideal? Even if they are, a wood screw still has to displace material on entrance... a machine screw would be a different story but let's not get into that. That's what the nut is for. 🙂

 

[GoodToGo]

You overcome friction while applying something and you overcome the same friction(in the opposite direction) while removing it?

 

[white]

i think the question is BS to begin with.

 

[LordRaiden]

Good arguments for each of the three answers so far. Well thought out. hehe. 😀

Now you see why it's so hard for me to decide on this answer?

 

[BigJelly]

"It takes an equal amount of force to apply an object as it does to remove it."
The idea in a more simple form can be stated as: it takes the same force to push a 60lb object as to pull the 60lb object.
Hammer a nail in then pull it out, its hard to do both ways.
Open a door and close it, requires the same amount of work--given it doesnt close/open by a closer/opener.
Screw in a screw, then unscrew it. Like the hammer/nail its hard both ways.


hence rule is absolute

 

[raptor13]

Originally posted by: white
i think the question is BS to begin with.

Blasphemy!!!


It makes you think. How can that be BS? And to answer your initial question, yes force is a vector. It has magnitude and direction.