Work and Kinetic Energy of weight

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SUMMARY

The discussion focuses on calculating the work done against friction for a 20.0-N weight sliding down a rough inclined plane at a 30.0-degree angle. The weight accelerates to a speed of 15.0 m/s after traveling 150 m. The initial calculation of approximately 2600 J was incorrect due to the misuse of forces in the work equation. The correct approach involves recognizing that friction is the non-conservative force that dissipates mechanical energy.

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Homework Statement



A 20.0-N weight slides down a rough inclined plane which makes an angle of 30.0o with the horizontal. The weight starts from rest and gains a speed of 15.0 m/s after sliding 150 m. How much work is done against friction? Use g = 10 m/s2.

Homework Equations



W = Fd cos θ

The Attempt at a Solution



I substituted it in the equation and got around 2600 J but the answer is wrong.

Can anyone help me out?

Thanks a lot before hand
 
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Try using conservation of energy.
150m is the hypotenuse, what is the length of the opposite side of the triangle formed?
 
rock_star said:

Homework Equations



W = Fd cos θ

The Attempt at a Solution



I substituted it in the equation and got around 2600 J but the answer is wrong.


That's because (for one) you used the wrong force.
a). What force is burning up your mechanical energy: gravity or friction?
b). Stated another way, Which force is non-conservative: gravity or friction?


(Here's a hint: "Work done against friction" = minus "the work done BY friction")
 

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