Exercise 6.4 actory worker pushes a 28.4 kg crate a distance of 4.5 m along a le

Question

Exercise 6.4 actory worker pushes a 28.4 kg crate a distance of 4.5 m along a level floor at constant velocity by pushing downward at an angle of 32 ° below the horizontal. The coefficient of kinetic friction between the crate and floor is 0.25 Part A What magnitude of force must the worker apply to move the crate at constant velocity? Express your answer using two significant figures AE Submit My Answers Give Up Incorrect; Try Again; 4 attempts remaining Part B How much work is done on the crate by this force when the crate is pushed a distance of 4.5 m Express your answer using two significant figures AE Submit My Answers Give U Part C How much work is done on the crate by friction during this displacement? Express your answer using two significant figures AE

Explanation / Answer

part 1 ) we are given that velocity is constant so the acceleration will be zero

---->>> Fsin(A) + mg - N = 0

---->>> Fcos(A) - uN = 0

and substitute the values of N we get

Fcos(A) - u(Fsin(A) + mg) = 0

Fcos(A) - usin(A) = umg

F = umg/(cos(A) - usin(A))

now we substitute the values given
F = 0.25 *28.4*9.8/(cos(32) - 0.25*sin(32))

F = 97.2374 N

part 2 ) How much work is done on the crate by this force when the crate is pushed a distance of 4.5 m? (in joules)

so work done is calculated by

W = 97.2374*cos(32)*4.5
W = 371.078 joules

part 3 ) How much work is done on the crate by friction during this displacement? (in joules)

work done will be same as in part 2 )

W=371.078 joules

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