Block sliding down an inclined plane and gravity

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Homework Help Overview

The discussion revolves around a problem involving a block sliding down an inclined plane, focusing on the forces acting on the block, including gravity and friction. The scenario includes specific parameters such as the mass of the block, the angle of the incline, and the coefficient of kinetic friction.

Discussion Character

  • Exploratory, Assumption checking, Conceptual clarification

Approaches and Questions Raised

  • Participants discuss the calculation of frictional force and the gravitational component acting on the block. There is an exploration of the implications of friction being greater than the gravitational component, leading to questions about the block's acceleration and motion.

Discussion Status

The discussion has revealed that one participant initially misinterpreted the relationship between friction and gravity, but another participant confirmed the observation about the forces, suggesting that the block is indeed decelerating as it slides down. There is an acknowledgment of the need to calculate the work done by both friction and gravity.

Contextual Notes

Participants are considering the initial conditions that may have imparted velocity to the block before it began sliding, which raises questions about the net forces acting on the block during its motion.

tbcreighton
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Homework Statement


There is a 5.0kg block sliding 1.5m down an inclined plane 12 degrees from the horizontal. the coefficient of kinetic friction is 0.310. Whats is the work done on the block by friction and gravity?


Homework Equations


F=ma, W=fd, fk=uk*N


The Attempt at a Solution


So, i calculated the frictional force to be mgcos(12)\mu_{k}, but when i found the component force of gravity in the opposite direction (mgsin(12)), i found that the force of friction was bigger than it. I think I am just overlooking something major, but i can't see what i did wrong.
 
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You didn't do anything wrong. You're right... the friction is greater than the component of gravity... this means the acceleration is up the plane...

So it is sliding downwards, but slowing down. net work done by friction and gravity will be negative.

Go ahead and calculate the work by friction and gravity.
 
DOH! of course. I feel really dumb now. Thanks for your help.
 
If I have understood the above correctly, some initial force must have been provided before it moved. That would have imparted the velocity, and the unbalanced force will decelerate it.
 

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