The box has a mass m and slides down the smooth chute having the shape of a parabola. If it has an initial velocity of v0 at the origin determine its velocity as a function of x. Also, what is the normal force on the box, and the tangential acceleration as a function of x?

Respuesta :

Answer:

[tex]v = \sqrt{v_{o}^{2}+2\cdot g\cdot a\cdot (x_{o}^{2}-x^{2})}[/tex],[tex]N = m\cdot \left[\frac{v_{o}^{2}+2\cdot g \cdot a \cdot (x_{o}^{2}-x^{2})}{\frac{\left[1 + 4\cdot a^{2}\cdot x^{2} \right]^{\frac{3}{2} }}{2\cdot |a|} } + \frac{g}{\sqrt{1+4\cdot a^{2}\cdot x^{2}}} \right][/tex], [tex]a = g \cdot \frac{2\cdot a \cdot x}{\sqrt{1+4\cdot a^{2}\cdot x^{2}}}[/tex]

Explanation:

An expression for the velocity can be derived by applying the Principle of Energy Conservation:

[tex]\frac{1}{2}\cdot m \cdot v_{o}^{2} + m\cdot g \cdot y_{o} = \frac{1}{2}\cdot m \cdot v^{2} + m\cdot g \cdot y[/tex]

[tex]\frac{1}{2} \cdot v_{o}^{2} + g \cdot y_{o} = \frac{1}{2} \cdot v^{2} + g \cdot y[/tex]

[tex]v = \sqrt{v_{o}^{2}+2\cdot g\cdot (y_{o}-y)}[/tex]

Let assume that chute is frictionless, so that box is moved because of gravity. The equations of equilibrium for the box are:

[tex]\Sigma F_{x'} = m\cdot g \cdot \sin \theta = m \cdot a\\\Sigma F_{y'} = N - m\cdot g \cdot \cos \theta = m\cdot \frac{v^{2}}{\rho}[/tex]

The expression for the radius of curvature and trigonometric functions are, respectively:

[tex]\sin \theta = \frac{dy}{ds} = \frac{1}{\sqrt{1+(\frac{dy}{dx} )^{2}} }\cdot \frac{dy}{dx}[/tex]

[tex]\cos \theta = \frac{dx}{ds} = \frac{1}{\sqrt{1+(\frac{dy}{dx} )^{2}}}[/tex]

[tex]\rho = \frac{\left[1 + (\frac{dy}{dx} )^{2} \right]^{\frac{3}{2}} }{\left|\frac{d^{2}y}{dx^{2}}\right| }[/tex]

Let assume that chute has the following form:

[tex]y = a\cdot x^{2}[/tex]

First and second derivatives of the function are, respectively:

[tex]\frac{dy}{dx}= 2\cdot a \cdot x[/tex]

[tex]\frac{d^{2}y}{dx^{2}} = 2\cdot a[/tex]

Trigonometric functions and radius of curvature are:

[tex]\sin \theta = \frac{2\cdot a \cdot x}{\sqrt{1+4\cdot a^{2}\cdot x^{2}} }[/tex]

[tex]\cos \theta = \frac{1}{\sqrt{1+4\cdot a^{2}\cdot x^{2}} }[/tex]

[tex]\rho = \frac{\left[1+4\cdot a^{2}\cdot x^{2}\right]^{\frac{3}{2} }}{2\cdot |a|}[/tex]

The velocity as a function of x is:

[tex]v = \sqrt{v_{o}^{2}+2\cdot g\cdot a\cdot (x_{o}^{2}-x^{2})}[/tex]

The normal force on the box as a function of x is:

[tex]N = m \cdot \left[ \frac{v^{2}}{\rho} + g\cdot \cos \theta \right][/tex]

[tex]N = m\cdot \left[\frac{v_{o}^{2}+2\cdot g \cdot a \cdot (x_{o}^{2}-x^{2})}{\frac{\left[1 + 4\cdot a^{2}\cdot x^{2} \right]^{\frac{3}{2} }}{2\cdot |a|} } + \frac{g}{\sqrt{1+4\cdot a^{2}\cdot x^{2}}} \right][/tex]

The tangential acceleration on the box as a function of x is:

[tex]a = g\cdot \sin \theta[/tex]

[tex]a = g \cdot \frac{2\cdot a \cdot x}{\sqrt{1+4\cdot a^{2}\cdot x^{2}}}[/tex]