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# Newtons second law Watch

1. A student is using a trolley and track to investigate the relationship between force and acceleration,

Question b) in such an experiment, the track is given a slight tilt to compensate for friction, why is this necessaries if the relationship by Newtons second law is to be demonstrated?

---------------------- (End of question for those who do not comprehend)

Newtons second law is: Resultant force= mass x acceleration

Friction is part of the resultant force and is that the reason why he is compensating for friction?
2. b u m p
3. What is it that you don't understand? You can't just post full questions, with zero attempt at a solution and expect people to just do your homework for you
4. I assume this means the track is tilted downwards slightly?

In basic calculations using Newton's laws we basically assume that friction is negligible. But if we actually did the experiments, friction would have an impact on the values we get out (as we don't have any friction- less motion in reality). Frictional force opposes the force due to mass x acceleration, so to compensate for this without actually calculating the frictional force, by tilting the track the component of the force in the horizontal direction will be increase as the truck will accelerate slightly more as it goes downhill, producing the same sort of force a truck on a perfectly horizontal frictionless surface.
5. (Original post by QUANTAM)
After Question B is my attempt and not part of the question, it's what I think of the problem. This is not homework either btw.
Fair enough.

Well, friction is one force, and it'll be acting in the direction opposite to which he is trying to accelerate.

If he's trying to investigate how a force acts to accelerate the trolley in one direction, then friction will provide a distortion to his results by providing a force in the opposite direction.

So in order to stop friction from interferring, he creates a slope, such that the force of gravity acting down the slope, exactly compensates the friction acting to stop the trolley moving down the slope. Then the frictional force and gravitational forces will sum to zero.

This means any acceleration obtained due to a force he exerts, will only be a result of his force and will have no contribution from friction, hence his result will be accurate.
6. (Original post by pianofluteftw)
I assume this means the track is tilted downwards slightly?

In basic calculations using Newton's laws we basically assume that friction is negligible. But if we actually did the experiments, friction would have an impact on the values we get out (as we don't have any friction- less motion in reality). Frictional force opposes the force due to mass x acceleration, so to compensate for this without actually calculating the frictional force, by tilting the track the component of the force in the horizontal direction will be increase as the truck will accelerate slightly more as it goes downhill, producing the same sort of force a truck on a perfectly horizontal frictionless surface.
So if he did not compensate for the friction, the resultant force would be less than the applied force right?
7. (Original post by QUANTAM)
So if he did not compensate for the friction, the resultant force would be less than the applied force right?
Yes, or in the context of the question a better way of putting it: if he didn't compensate for friction, the force he measured would be less than the force calculated using Newton's laws.

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Updated: May 14, 2013
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