serenity3111
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 5) You did 170 joules of work lifting a 140 N backpack. How high did you lift the backpack?          

6)  in problem 5 how much did the backpack weigh in pounds (hint there are 4.45 newtons in one pound)

Respuesta :

austinbaird
sorry im from the UK, ill do my math in metric  :) 
5) work done = force * distance moved in direction of force

170J = 140N* ?d
170J/140N = 1.21m 

F=Ma

140N/9.81ms^-2=

14.27Kg or 31.46Ib

you could do the fast alternative simplified route to this question 

as 140/4.45 = 31.46Ib

Answer:

d = 1.21 meters

The mass of the backpack is 31.48 pound.

Explanation:

(5) Work done in lifting a backpack, W = 170 J

The force acting on the backpack, F = 140 N

The work done by an object is given by :

[tex]W=F\times d[/tex]

d is the height at which the backpack is lifted

[tex]d=\dfrac{W}{F}[/tex]

[tex]d=\dfrac{170\ J}{140\ N}[/tex]

d = 1.21 meters

So, the backpack is lifted to a height of 1.21 meters.

(6) If m is the mass of the backpack. It can be calculated as :

W = mg

[tex]m=\dfrac{W}{g}[/tex]

[tex]m=\dfrac{140}{9.8}[/tex]

m = 14.28 kg

Since, 1 kg = 2.204 pound

14.28 kg = 31.48 pound

So, the mass of the backpack is 31.48 pound. Hence, this is the required solution.

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