I was working on a problem with an incline plane and two masses connected by a pulley. One mass on the plane and the other hanging down the side. We had to first calculate the acceleration ignoring friction and then we were give a coefficient of kinetic friction and asked to recalculate acceleration accordingly.(adsbygoogle = window.adsbygoogle || []).push({});

When I did the second part the magnitude of my acceleration was greater than when there was no friction. I'm wondering if this makes sense. Thinking solely in terms of F=ma it makes sense that if the force is greater but the mass stays the same the magnitude of the acceleration will be greater than with smaller forces. I am thinking that with regard to a problem as this with an incline plane and kinetic friction the tension (the force upward) in the pulley is directed along the x axis (up the plane) and the forces opposing this are the force of friction downward (negative x axis) and the sine of the angle times the mass x g of the object on the plane. Therefore, the force up the plane (the tension) isgreaterwith friction involved than it is w/o friction because it must be greater than the two forces opposing it for any acceleration to happen. Therefore, it makes sense that the magnitude of acceleration is greater than w/o friction.

However, intuitively, it feels strange. It seems odd that when there is friction involved the masses would have greater acceleration than if there was no friction opposing the acceleration.

Any help explaining this to me? Am I right on my thoughts above and just need to "correct" my intuition or is my intuition correct and therefore, the magnitude of the acceleration should be less with kinetic friction than w/o friction and I need to rework my problem accordingly? Thanks!

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# ? on Kin. friction/no friction and mag. of acceleration intuition

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