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

given.

mass of the crate m=28.4 kg

distance travelled s=4.5 m

velosity is constant

angle of incline, theta = 32 oC

uk=0.25

A)

if the crate is moves with constant velocity,

applied force F=(uk*mg)/[cos(theta)-uk*sin(theta)]

=(0.25*28.4*9.8*)/[(cos(32)-0.25*sin(32)]

=69.58/(0.7155)

=97.24 N

B)

w=F*s

=97.24*4.5

=437.57 J

C)

W=fK*s

=(uk*mg)*s

=(0.25*28.4*9.8)*4.5

=313.11 N

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