Physics Photo of the Week
Thrust from a fire extinguisher - By Eri Watanabe
In this experiment, the
rider holds a CO2 fire extinguisher and discharges it
towards the back while he rides on the cart. The rider should
continuously hold the fire extinguisher as the cart glides past the
camera. The camera recorded a video of the motion and we analyzed
The graphs of the motion of the cart are shown below. On the left
is the position vs. time. In this graph we can see that as time
increases, the distance the cart moves also increases, meaning that the
cart travels with greater and greater speed.
|The position vs time shows that
as time increases, the incremental distance increases, indicating that
the mass accelerates
|The velocity vs time shows a
steady increase in the velocity indicating that the acceleration is
In addition, we made another graph. This new graph (right) shows
the velocity of the cart vs. time. Both of graphs are not
completely accurate, because of my marking the points. On the
right-hand graph of velocity vs. time, the velocity increases as time
increases. Note that the slope of the velocity vs. time graph is
a constant. The slope of the velocity equals the acceleration,
and this means that the acceleration is constant. In this
experiment, Newton’s second law is seen: with constant force (thrust),
acceleration is constant. Acceleration = thrust/mass.
Many thanks to Terry Payne of the Public Safety Department for
recharging the fire extinguisher.
Photo of the
published weekly during the academic year on Fridays by the Warren
Wilson College Physics
Department. These photos feature an interesting phenomena in
the world around us. Students, faculty, and others are invited to
submit digital (or film) photographs for publication and
explanation. Atmospheric phenomena are especially welcome.
Please send any photos to firstname.lastname@example.org.
here to see the Physics Photo
the Week Archive.
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