Boost? 1:28 PM www.webassign.net 4 Need Help? Lead 17. -/2 points SerCP10 4.P 04

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Boost? 1:28 PM www.webassign.net 4 Need Help? Lead 17. -/2 points SerCP10 4.P 041 My Notes Ask Your Teach A 1,240-N crate is being pushed across a level floor at a constant speed by a force F of 310N at an angle of 200 below the horizontal, as shown in the figure a below 20. 20? (a) What is the coefficient of kinetic friction between the crate and the floor? (Enter your answer to at least three decimal places) (b) If the 310-N force is instead pulling the block at an angle of 20.0 above the horizontal, as shown in the figure b, what will be the acceleration of the crate? Assume that the coefficient of friction is the same as that found in part (a) Need Help? 18. +-/1 points SerCP104.P045.ML . My Notes Ask Your Teach Objects with masses mi . 110kg and m2 . 80 kg are connected by al gringthat passes over a frictionless pulley as in the figure below. If, when the system starts from rest. m2 falls 1.00 m in 155 determne the coefficient of kinetic friction between m, and the table. Need Help?ReaditMaster

Explanation / Answer

17)

the frictional force acting is

fk = f*cos(theta)

fk = 310 N x cos(20)

fk = 291.3 N

The normal force acting on block is

n = W + f*sin(theta)

n = 1240 + 310*sin(20)

n = 1346 N

Therefore coefficient of fraction is

u = fk/n

u = 291.3 N / 1346 N

u = 0.2164

b)

the frictional force acting on block is

fk = uN

fk = u(W - f*sin(theta)

fk = 0.2164(1240 - 310*sin(20))

fk = 245.4 N

The acceleration is

a = (F*cos(20) - fk)g / W

a = (310*cos(20) - 245.4) / 1240

a = 0.148 m/s^2

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