- #1

BriannaUND

- 12

- 0

1) A train normally travels at a uniform speed of 72 km/hr on a long stretch of straight, level track. On a particular day, the train must make a 2.0-min stop at a station along this track. If the train decelerates at a uniform rate of 1.0m/s2 and, after the stop, accelerates at a rate of .5 m/s2, how much time is lost because of stopping at the station?

So far I have calculated vo= 72 km/hr (.278 m/s divided by 1 km/hr) = 20.0 m/s. Then t= v-vo/a = 0-20 m/s divided by -1.0 m/s2 = 20 sec to stop. Does this look correct? And how do I go about calculating the time lost?

2)The driver of a pickup truck going 100 km/hr applies the brakes, giving the truck a uniform deceleration of 6.5 m/s2 while it travels 20.0 m. a) what is the speed of the truck in km/hr at the end of this distance? and b) how much time has elapsed?

3) An earthquake releases two types of traveling waves, called transverse and longitudinal. The average speeds of transverse and longitudinal seismic waves in rock are 8.9 km/s and 5.1 km/s respectively. A seismograph records the arrival of the transverse waves 73 s before that of the longitudinal waves. Assuming that the waves travel in straight lines, how far away is the center of the earthquake from the seismograph?

Thanks again!