a train slows down from 80 kilometer per hour with a uniform retardation of 2 meters per second.How long will it take to attain a speed of 20 kilometers per hour?
+118608 I am not sure if you want me to do this with calculus or with physics formulas.
I'll do it with physics formula.
$$\\u=80km/hour\;=\frac{80000}{60*60}m/sec = \frac{200}{3*3}m/sec= \frac{200}{9}m/sec\\\\
v=20km/hour\;=\frac{20000}{60*60}m/sec = \frac{50}{9}m/sec\\\\
a=-2m/s^2\\\\
find\;t\\\\
v=u+at\\\\
\frac{50}{9}=\frac{200}{9}+-2t\\\\
\frac{-250}{9}=-2t\\\\
\frac{250}{18}=t\\\\
t=13.9\;sec \qquad \mbox{to nearest one tenth of a second}\\\\$$
+118608 I am not sure if you want me to do this with calculus or with physics formulas.
I'll do it with physics formula.
$$\\u=80km/hour\;=\frac{80000}{60*60}m/sec = \frac{200}{3*3}m/sec= \frac{200}{9}m/sec\\\\
v=20km/hour\;=\frac{20000}{60*60}m/sec = \frac{50}{9}m/sec\\\\
a=-2m/s^2\\\\
find\;t\\\\
v=u+at\\\\
\frac{50}{9}=\frac{200}{9}+-2t\\\\
\frac{-250}{9}=-2t\\\\
\frac{250}{18}=t\\\\
t=13.9\;sec \qquad \mbox{to nearest one tenth of a second}\\\\$$
