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# equal and opposite forces watch

1. so two objects interacting exert equal and opposite forces... but surely that should cancel out and leave the object stationary so how does movement occur? and when a car exerts equal and opposite forces, it is stationary or going at a constant speed? Is their no overall resultant force when a car is going at constant speed but theirs equal and oppsoite forces? Its so hard to get your head around what force is exerted where and what type of movement these equal and opposite forces cause.
2. It's to do with the different masses of the objects I think. There's the same force on both objects but because one is lighter it will move more that the other.

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3. Newton's First Law states that an object will remain at rest or in uniform motion in a straight line unless acted upon by an external force. Acceleration(either positive or negative) is caused by the unbalancing of forces.
4. (Original post by Mayhem™)
Newton's First Law states that an object will remain at rest or in uniform motion in a straight line unless acted upon by an external force. Acceleration(either positive or negative) is caused by the unbalancing of forces.
so is their still equal and balanced forces on a stationary object? on any object? what causes it to move are other forces apart from the equal and opposite forces?
5. (Original post by mygcserevision)
so two objects interacting exert equal and opposite forces... but surely that should cancel out and leave the object stationary so how does movement occur? and when a car exerts equal and opposite forces, it is stationary or going at a constant speed? Is their no overall resultant force when a car is going at constant speed but theirs equal and oppsoite forces? Its so hard to get your head around what force is exerted where and what type of movement these equal and opposite forces cause.
Take an accelerating car on a level road.
There are pairs of forces balanced such as weight and reaction force of the road which are equal and opposite forces which must be balanced (as the car is neither flying nor sinking into the road).
However, the thrust of the car along the road is greater than the opposing force of the friction plus the air resistance/drag of the car in the other direction.
Therefore there are equal and opposite forces which are balanced but there is an overall unbalanced force on this car, so it accelerates.
EDIT: I understand why this is confusing, some people in my AS Physics class couldn't understand it, I do hope this clears something up!
Spoiler:
Show
This is due to Newton's 1st Law : An object will only change in velocity if a resultant force acts on it
And Newton's 2nd Law: If object A exerts a force on object B, then object B will exert an equal and opposite force on object A

btw Mayhem™ for a good 1st law definition too
6. (Original post by mygcserevision)
so is their still equal and balanced forces on a stationary object? on any object? what causes it to move are other forces apart from the equal and opposite forces?
a stationary object has equal forces acting upon it from all sides, once one of the forces changes(this can be an increase or decrease), the object will move towards the source of the weaker force until the forces are balanced again
7. When you walk, the force you exert on the floor (the earth) is exactly the same as the force the earth exerts on you. Obviously though the directions are opposite. But think about it F=ma, and the mass of the earth is on the order on 1027 kg whereas a person is around 50-100 kg on average. So the person walking will accelerate quite a lot relative to the acceleration of the earth which is unmeasurable, the acceleration of the Earth cause by a person walking is so small it could never be measured.
However it is important to note that a person walking does cause the Earth to accelerate, crazy as that sounds if you've never considered it before.

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Updated: January 25, 2016
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