Ok, I know that if an object is moving at a constant velocity on a frictionless

Question

Ok, I know that if an object is moving at a constant velocity on a frictionless surface, the forces are balanced (add to 0). The only force vectors you would have are Fg and Fn going down/up.

But what if an object is being dragged across a frictionless surface with a string; wouldn't there be a tension force going left or right? So if you add that tension force, I don't see how the forces in the x-direction can be balanced... because shouldn't there be a force going the opposite way so the forces still add to 0?

Thank you!
PS. if the string broke, would the object keep moving with a constant speed since there is no friction?

Explanation / Answer

So if I understand correctly, you have a block with a string. Your right in saying that the component in the y direction adds to zero otherwise the object would float or go into the surface. However, in the x direction if a force is applied the the block will accelerate in the way the string is pulled and will not stop if frictionless. This is because all of the energy will continue in the same direction because there is no opposite force. (An object in motion will stay in motion unless some force acts on it.) Forces are not required to equal zero if the block is accelerating. and you are correct if the string broke it would continue forever until something acted on it. Hope this helps.

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