A 5000-lb wrecking ball hangs from a 50-ft cable of density 10 lb/ft attached to a crane. Calculate the work done if the crane lifts the ball from ground level to 50 ft in the air by drawing in the cable.

Respuesta :

Answer:

total work is = 52450 J

Explanation:

given data

mass =  5000-lb

density = 10 lb/ft

height = 50 ft

solution

as we will treat here cable and ball are separate  

and

here work need to lift cable is

w = (10Δy )(9.8 y )  j

and

now summing all segment of cable

so passing limit Δy to 0

so total work need

= [tex]\int\limits^{10}_0 {98y} \, dy[/tex]    

= [tex][49 y^2]^{50}_0[/tex]

= 2450J

so lifting 5000 lb wrcking 50 m  required additional 5000 + 2450

so total work is = 52450 J

The work done if  the crane lifts the ball from ground level to 50 ft in the air by drawing in the cable is [tex]3.39 \times 10^5 \ J[/tex].

The given parameters;

  • mass of the ball, m = 5000 lb
  • height of the cable, h = 50 ft
  • density of the cable, ρ = 10 lb/ft

The work done if  the crane lifts the ball from ground level to 50 ft in the air by drawing in the cable is calculated as follows;

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

where;

  • g is acceleration due to gravity = 32.17 ft/s²

The work done is calculated as;

[tex]W = 5000 \times 32.17 \times 50\\\\W = 8,042,500 \ lb-ft^2/s^2\\\\W = \frac{0.13825 \ J/m}{1 \ lb.ft/s^2} \times 8,042,500 \ lb.ft^2/s^2\\\\W = 1,111,875.63 \ \frac{J-ft}{m} \times \frac{1 \ m}{3.28 \ ft} \\\\W = 338,986.47 \ J[/tex]

Thus, the work done if  the crane lifts the ball from ground level to 50 ft in the air by drawing in the cable is [tex]3.39 \times 10^5 \ J[/tex].

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