A 15.0-m length of hose is wound around a reel, which is initially at rest. the moment of inertia of the reel is 0.570 kg·m2, and its radius is 0.170 m. when turning, friction at the axle exerts a torque of magnitude 3.50 n·m on the reel. if the hose is pulled so that the tension in it remains a constant 29.0 n, how long does it take to completely unwind the hose from the reel? neglect the mass of the hose, and assume that the hose unwinds without slipping.

Respuesta :

Answer:

t  = 8.391s

Explanation:

we know that:

T = Iα

where T is the torque, I the moment of inertia and α the angular aceleration. So:

Fr-[tex]T_k[/tex]  = Iα

where F is the tension of hose, r the radius and [tex]T_k[/tex] is the torque exerts by the friction.

Then, replacing the data:

(29N)(0.17m)-(3.5n*m)=(0.57kg*m^2)α

solving for α:

α = 2.508 rad/s^2

we also know that:

a = αr

where a is the linear aceleration, so:

a = 2.508rad/s*0.17m

a = 0.426 m/s^2

Finally:

x = [tex]\frac{1}{2}at^2[/tex]

where x is the large of the hose, a the linear aceleration and t the time. Replacing values:

15m = [tex]\frac{1}{2}(0.426)t^2[/tex]

Solving for t:

t  = 8.391s