Question

(Person pushing box up rough ramp) The conveyor belt broke! The unlucky FedEx employee must

now push 100 boxes up a 5 meter-long (along the ramp) rough ramp that is inclined 15 degrees above

the horizontal. The person pushes parallel to the ramp. Let's say each box has a mass of 50 [kg] and

the coefficient of kinetic friction each box and the ramp is 0.15

a) If the employee is on a tight schedule and only has 6 minutes to load all the boxes. How much time

does she have per box?

b) Subtract 100 seconds from the 6 minutes available in part (a) to account for the time it takes the

employee to grab the next box. How much time does the employee have to slide a box up the ramp?

c) If each box starts at the bottom of the ramp at rest, find the necessary acceleration of each to make it

up the 5 [m] long ramp in the time you found in part (b).

d) Draw a complete FBD of the box while it is being pushed up the ramp.

e) Use your FBD from part (d) to find the magnitude of the pushing force the employee must exert on

each box. This is the minimum force the person must exert in order to load all 100 boxes in 6 minutes.

Answer 1

(a)There are 100 boxes to load under 6 min

so time for 1 box =6*60/100 =3.6 sec per box

ANSWER: 3.6 s

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(b)Now total time is reduced to 6*60-100 =260sec

so time for 1 box =260/100 =2.6 sec per box

ANSWER: 2.6s

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(c)distance to cover =5m and available time is 2.6 s

Use formula s=ut+1/2at²

initial velocity is zero

ANSWER: a =1.48 m/s²

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(d)

(e)Net Force =mass*acceleration

Only unknown is F

ANSWER:

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