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Solved Problem on Kinematics

A motorcyclist moves in the opposite direction of an oriented frame of reference, the magnitude of its speed is 40 m/s, and initially, his position is −150 m. Find:

a) The displacement as a function of time;

b) In what time it passes the origin.

Problem data

- speed of the motorcyclist: |
*v*| = 40 m/s; - position at initial time:
*S*_{0}= −150 m.

We choose a reference frame with the positive direction oriented to the right.

Solution

a) We want to find a function of the type

\[ \bbox[#99CCFF,10px]
{S=S_{0}+vt}
\]

the initial position is given in the problem,
\[ \bbox[#FFCCCC,10px]
{S=-150-40t}
\]

b) When the motorcyclist passes through the origin we have

\[
0=-150-40t\\
40t=-150\\
t=-\frac{150}{40}\\
t=-3.75\;\text{s}
\]

as there is no negative time, this means that the motorcyclist
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Fisicaexe - Physics Solved Problems by Elcio Brandani Mondadori is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License .