Friction versus Gravity (Work on an Incline)

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SUMMARY

The discussion focuses on calculating the work done by gravity and friction on a 5kg block sliding down a 12-degree incline with a coefficient of kinetic friction (μk) of 0.31. The calculations presented indicate that the work done by gravity is -15.29J and the work done by friction is 22.29J. The confusion arises from the use of the sine and cosine functions for angles, specifically using sin(348) and cos(348) instead of their respective values for 12 degrees. The correct approach involves identifying the gravitational force components acting parallel and normal to the incline.

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  • Understanding of basic physics concepts such as work, energy, and forces.
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  • Knowledge of the coefficient of friction and its application in physics.
  • Ability to perform calculations involving gravitational force components on an incline.
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  • Review the principles of work and energy in physics.
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Ronnin
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Can someone verify my calculations here? I have a 5kg block on an incline plane 12 degrees down angle. Mu k is .31 and slides a distance of 1.5m down the ramp.

Work gravity=5k(9.8 m/s^2)sin(348)(1.5m)=-15.29J
Work friction=.31(5k(9.8 m/s^2)cos(348)(1.5m)=22.29J

This can't be right, can it?
 
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Why sin or cos of 348, which looks like 360°-12°?

Work, like energy, is a scalar.

Work is given by the force applied over a distance.

One must assure the force is correctly characterized. Find the component of the gravitational force (weight) acting parallel with the incline. The friction is proportional (via friction factor) to the gravitational force component acting normal to the incline.

http://hyperphysics.phy-astr.gsu.edu/hbase/N2st.html
 
Astronuc said:
Why sin or cos of 348, which looks like 360°-12°?

Work, like energy, is a scalar.

Work is given by the force applied over a distance.

One must assure the force is correctly characterized. Find the component of the gravitational force (weight) acting parallel with the incline. The friction is proportional (via friction factor) to the gravitational force component acting normal to the incline.

http://hyperphysics.phy-astr.gsu.edu/hbase/N2st.html

I used 348 because the slope is downward from 0. Is any of my math wrong?
 

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