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Motion In A Plane

Question
CBSEENPH11020303

A particle of mass m is at rest at the origin at time t = 0. It is subjected to a force F (t) = F0e–bt in the x direction. Its speed v(t) is depicted by which of the following curves?

Solution

C.

straight F equals space straight F subscript 0 straight e to the power of negative bt end exponent
rightwards double arrow space straight a space equals space straight F over straight m space equals space straight F subscript 0 over straight m straight e to the power of negative bt end exponent
rightwards double arrow space dv over dt space equals straight F subscript 0 over straight m straight e to the power of negative bt end exponent
integral dv space equals space integral subscript 0 superscript straight t straight F over straight m straight e to the power of negative bt end exponent dt
rightwards double arrow space straight v space equals straight F over straight m open square brackets table row cell negative 1 end cell row straight b end table close square brackets open square brackets table row cell straight e to the power of negative bt end exponent end cell end table close square brackets subscript 0 superscript straight t
rightwards double arrow space straight v equals space straight F over mb left square bracket straight e to the power of negative bt end exponent right square bracket
straight v equals space 0 space at space straight t equals space 0
and space straight v rightwards arrow space straight F over mb space as space straight t rightwards arrow infinity
So, velocity increases continuously and attains a maximum value of v= F/mb as t ∞