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I have four objects with identical mass and radii, but different shapes, and exert the same torque on each. Rank these four objects according to their final rotational velocities after 30 seconds of this applied torque: A) A solid cyllander B) A hoop C) A solid Sphere D) A hollow Sphere

Respuesta :

The Newtos's second law and kinematics for the rotational movementa llows to find the result for the order of the velocities of the bodies is:  

       hoop < hollow sphere < solid cylinder < solid sphere

Newton's second law for rotational motion states that the net torque is proportional to the moment of inertia and the angular acceleration of the body.

           ∑ τ = I α

where the bold letters indicate vectors, τ is the torque, I the moment of inertia and α the angular acceleration.

The moments of inertia of bodies with high symmetry are tabulated.

Solid cylinder      I = ½ m R²

ring                      I = m R²

Solid sphere       I = [tex]\frac{2}{5}[/tex] m R²

hollow sphere    I = ⅔ m r²

look for the acceleration of each object.

A) Solid cylinder.

            [tex]a_1 = 2 \frac{\sum \tau }{m R^2}[/tex]  

            a₁ = 2 a₀

B) hoop or Ring.

            [tex]a_o = \frac{\sum \tau}{m R^2}[/tex]

C) Solid sphere.

            [tex]a_2 = \frac{5}{2} \ \frac{\sum \tau}{m R^2 }[/tex]  

            a₂ = 2.5 a₀

D) Hollow sphere.

           [tex]a_3 = \frac{3}{2} \ \frac{\sum \tau}{mR^2 }[/tex]  

           a₃ = 1.5 a₀

if the bodies leave with the same initial velocity, the acceleration determines which one goes faster.

           w = w₀ + α t

suppose that the initial speed is zero.

           w = α t

Let us calculate the velocity for the bodies after 30 s.

hoop.

           w = 30 a₀

solid cylinder.

            w = 60 a₀

solid sphere.

            w = 75 a₀

hollow sphere.

            w = 45 a₀

In conclusion using Newton's second law and kinematics for rotational movement we can find the result for the order of the velocities of the bodies are:  

       hoop < hollow sphere < solid cylinder < solid sphere

Learn more here:  brainly.com/question/24692653

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