a particle of mass m sits at rest at x = 0. At time t = 0 a force given by F = Fe^(-t/T) is applied in the +x direction; F and T are constants. When t = T the force is removed. At this instant when the force is removed, (a) what is the speed of the particle and (b) where is it?

Respuesta :

Explanation:

Given:[tex]F=m\ddot{x}=Fe^{-\frac{t}{T}}[/tex]

Solving for [tex]\ddot{x}[/tex]:

[tex]\ddot{x}=\frac{F}{m}e^{-\sqrt{\frac{F}{m} } t}[/tex]

where:

[tex]T=\sqrt{\frac{m}{F}}[/tex]

Integrating to get [tex]\dot{x}[/tex] with initial conditions [tex]\dot{x}(0)=0[/tex]:

[tex]\dot{x}=\sqrt{\frac{F}{m}}-\sqrt{\frac{F}{m}} e^{-\sqrt{\frac{F}{m}} t}[/tex]

Integrating to get x with initial conditions x(0) = 0:

[tex]x=-1+\sqrt{\frac{F}{m}} t+e^{-\sqrt{\frac{F}{m}}t}[/tex]

When t=T:

[tex]x=-1+\sqrt{\frac{F}{m}}\sqrt{\frac{m}{F}}+e^{-\sqrt{\frac{F}{m}}\sqrt{\frac{m}{F}}}=\frac{1}{e}[/tex]

[tex]\dot{x}=\sqrt{\frac{F}{m}}-\sqrt{\frac{F}{m}} e^{-\sqrt{\frac{F}{m}}\sqrt{\frac{m}{F}}}=\sqrt{\frac{F}{m}}(1-\frac{1}{e})[/tex]