Calculating the Velocity of a Block on an Inclined Plane with Friction

AI Thread Summary
The discussion focuses on deriving the velocity of a block moving up an inclined plane with friction. Two expressions for velocity are presented, leading to confusion about their correctness. The first expression accounts for the initial kinetic energy, gravitational potential energy, and work done against friction, while the second includes an additional gravitational term, leading to different results. Participants are encouraged to clarify their calculations and reasoning behind each expression. Understanding the derivation process is emphasized to resolve the discrepancies in the answers.
monarchus
A block of mass m is pushed off with an initial speed u so that it moves up a rough plane inclined at an angle @ to the horizontal. the friction between the block and the plane is R. Deduce an expression for the velocity v of the block after it has moved a distance d along the inclined plane. Explain any additional symbols in your expression.


which is correct:

(1) 1/2mu^2 - mgd sin @ - Rd = 1/2mv^2
v = [ (mu^2 - 2mgd sin @ - 2Rd) / m]^1/2

(2) 1/2mu^2 - mgd sin @ - Rd = mgd sin @ + 1/2mv^2
v = [ (mu^2 - 4mgd sin @ - 2Rd) / m]^1/2


AND WHY?

thank you.
 
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Are you asking us to do you homework for you?
 
Topher925 said:
Are you asking us to do you homework for you?



well, i did it. Just get different answer from the answer given. Asking why is it like that because i don't understand, is this called asking you all to do my homework for me? well, personally, i don't think so. but if you think so, then it's fine with me. I'll apologize.
 
Why don't you explain how you arrived at each expression?
 

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