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Mechanics

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4 Dec 2008 12:11:12 IST

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Inclined plane question

None

Two packages start sliding down a 20 degrees ramp from rest at a distance d = 6.6 m alon the ramp from the bottom. Package A has a mass of 5.0 kg and a coefficient friction 0.20. Package B has a mass of 10 kg and a coefficient friction 0.15. How long does it take package A to reach the bottom?

Attempt:

I was thinking about this equation to use

Acceleration of a body sliding on an inclined plane:

a = g sin theta (1 - mewk cot t^2)

but I dont know if I can use that equation. Is there a better way to solve this problem? Please help someone.

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Comments (2)

aagu97

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Joined: 19 Jan 2007

Posts: 7

4 Dec 2008 13:35:11 IST

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ya u can definitely apply the equations

in fact its the only means bu which u can solve

by free body diagram u get that result only

and since we have to calculate time we cant use work enegy concepts

▬●๋•kểểp کmílíńg álwáýک●๋•▬•

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Joined: 11 Sep 2008

Posts: 101

4 Dec 2008 13:56:00 IST

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@ aakash, y u mention about B, i think deir iz no need and use of B. / OR may b i can't able to understand ur Q.

4m FBD diagram of A,

g sin - $gcos = a

g sin20⁰ - 0.2 X g X cos20⁰

so, a = g X 0.342 - g X 0.2 X 0.9397

= 0.1541g

as , u = 0,

so, S = 1/2 a t²

=> 6.6 = 1/2 X 0.1541 g X t²

if we take g = 9.8 , then time taken 2 reach A into bottom = t =[( 6.6 X 2)/0.1541 X9.8 ]^1/2

= ( 8.7)^1/2

= it is approx 3 second

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