Friction versus Gravity (Work on an Incline)

[Ronnin]

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?

 

[Astronuc]

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

 

[Ronnin]

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?