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About LinkBacksI'm just confused by the question TBH
I'm just confused by the question TBH
exactly, to me the quesiton pretty much says balanced = unbalanced.....how is this possible
"if every force has an equal but opposite reaction then how can forces be unbalanced"
Well, I take 'unblaanced force' to mean something like the following.
Set of scales, one side has 2KG and the other side has 1KG.
From a central position, the foces would be unbalanced so the 2KG would go down and the 1Kg would go up.
However, actuall action of one side going down is found equally in the other side going up.
Sp, unblanaced forces AND equal and oposite actions, unless I'm barking up totally the wrong tree.
ok you need to be able to look at various components of an 'unbalanced' force.
Imagine a hand throwing a ball.
The hand exerts a force on the ball and the ball must exert an equal and oposite force on the hand acording to Newton's First Law.
Because there is a net force acting on the ball it undergoes acceleration of the magnitude F = ma in the direction of the force coming from the hand.
There is a force acting on the hand from the ball but it does not accelerate backwards as there is the same force still pushing the hand forward from the arm.
as for the ball falling through the air thing...
Initially, when you drop the ball the only force acting on the ball is gravitaion pull of the earth. Gravity causes an acceleration of g (9.81) for the net force on the ball is Fo = mg.
As the ball falls faster the resistance from the air increases until the ball approaches terminal velocity. At the terminal velocity the resistance force from the air is equal to Fo from above. There is a downwards force of F=mg and an upwards force of F=mg so the net force = 0 and there is no more acceleration.
It's difficult to apply Newton's First Law in this situation, the force acting on the ball is the gravitational force of theEarth acting upon the ball - there is an equal and opposite reaction though, the ball pull on the Earth with an equal force in the opposite direction!
Hope this helps
That's not the best way to put it. The force coming back from the ball will be transfered as a change in velocity in equal amounts to the change in velocity of the ball.Originally Posted by Dr. X
Acceleration is considered unbalanced because there is a greater force pushing it than there is pulling it back, otherwise it wouldn't be gaining in speed.
If it was going at a constant speed, then there would be an equal force forward/backwards.
Right, if that's the defenition it's got feck all to do with equal and oposite reactions. Just a case of another teacher in need of some lessons.
Well, thats just how I remember our physics teacher explaining it. He said something about this:
If a car is going at a constant speed, no more force is need to keep it like that.
If it's accelerating, more force is needed.
I really don't see what is so unbalanced about acceleration. If you draw force diagrams, it does take a net force to accelerate an object...locally. If you increase your frame of reference, you can always find the 'equal and opposite' reaction within the larger system.
oh this thread has just reminded my why i got out of engineering after college
oh jeeez,
Yes, but as the earth weighs 5700 billon billon tonnes, it does not accelarate much. f=ma still applies though.
Consider the example of you dropping the ball from a height. Gravity creates a force of attaction between the ball and the earth. Both are attacted to each other, and both begin accelarating towards each other untill they collide. It only appears as if the ball's accelaration in unbalaced becase the observer is on the earth, and the earth's accelaration is very small.
Chrestomanci Has hit the nail on the head. Ther is an equal an opposite force but this acceleration is so small that you do not notice it due to the mass of the earth.
What you have to be careful of is the what each force is relative to.
Physics is one of those science subjects that like to get all philosophical and artys. Yuk! I did get a great grade for it at A level however so I cant complain.
erm - post #9
Pardon? Physicists arent very much into philosophy as a rule, however, philosophers like to think they know everything there is to know about wuantum mechanics and relativity from reading univers in a nutshell and brief history of time, and thus are entitled to make me write essays about why special relativity is wrong, which is obvious, but im not allowed to mention general relativity, because thats 'outside the scope of the course'. scarf wearing girly men the lot of them
</rant>
I sence some bitterness there
i do apologise konan555 u did meantion it first. Christ made a more detailed explaination of it so I gave him sum creds.
But credit wher credits due bro.
Philosophers are strange strange people. Imagine getting paid just to think up random crap and be all controversial. Wonderful.
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