A platform is free to rotate in the horizontal plane about a frictionless, vertical axle. About this axle the platform has a moment of inertia Ip. An object is placed on a platform a distance R from the center of the axle. The mass of the object is m and it is very small in size. The coefficient of friction between the object and the platform is μ. If at t = 0 a torque of constant magnitude τ0 about the axle is applied to the platform when will the object start to slip?

Respuesta :

Answer:

It will start to slip at [tex]t=\sqrt{\frac{\mu*g}{R}}*\frac{I_p+m*R^2}{\tau_0}[/tex]

Explanation:

We can find the angular acceleration from a sum of torque on the system:

[tex]\tau_0=\alpha *(I_p+m*R^2)[/tex]  Solving for α

[tex]\alpha =\frac{\tau_0}{I_p+m*R^2}[/tex]

Now, on the object, we make a sum of forces on the centripetal-axis:

[tex]Ff=\mu*N=m*a=m*\frac{V^2}{R} =m*\omega^2*R[/tex]   Solving for ω:

[tex]\omega=\sqrt{\frac{\mu*N}{m*R} }[/tex]

From a sum of forces on the axis perpendicular to the platform:

[tex]N-m*g=0[/tex]   [tex]N=m*g[/tex]

Replacing this value into the ω equation:

[tex]\omega=\sqrt{\frac{\mu*g}{R} }[/tex]  Now we have to find the amount of time that takes to the object to get this speed.

[tex]\omega=\alpha *t[/tex]   Solving for t:

[tex]t=\frac{\omega}{\alpha} =\sqrt{\frac{\mu*g}{R}}*\frac{I_p+m*R^2}{\tau_0}[/tex]