Amotor drives a disk initially at rest through 25.9 rotations in 5.0 s. assume the vector sum of the torques caused by the force exerted by the motor and the force of friction is constant. the rotational inertia of the disk is 4.0 kg⋅m2. when the motor is switched off, the disk comes to rest in 12 s.
a.)what is the magnitude of torque created by the force of friction?
b.)what is the magnitude of torque caused by the force exerted by the motor?

Answer

given,

rotation of disk is equal to(θ) = 25.9

time taken = 5 s

moment of inertia of disk = 4 Kg.m²

disk come to rest in = 12 sec

a)  θ = 2 π x 25.9

    θ = 162.73 rad

    using equation of rotational motion

     θ =  ω₀t + 0.5 α t²

     162.79 =  0 + 0.5 x α x 5²

      α = 13.02 rad/s²

total torque acting

again using the rotational equation

when only friction is acting angular acceleration

now torque due to friction

now,

if the forces acting on an object are unbalanced, the object will accelerate in the direction of the net force on the object.

explanation:

this is best explained by having an understanding of newton's second law, which states that f=ma. you see, when the forces are unbalanced, net force (sum of all forces) is not zero. therefore making it necessary for the object to have an acceleration in the direction of the net force.

and 1and 1