A train leaves the train station at noon and travels at a constant speed of vt = 50 mi/hr on a straight track. 2 hr later, a car
leaves the same train station and travels in the same direction at vc = 70 mi/hr on a road next to the train track. How far from the station is the place where the car catches up with the train? x =
When the car starts 2 hours later, the train would have a head start of
50 * 2 = 100 miles
The speed of the car relative to the train is
70 - 50 = 20 mi/hr
For the car to catch up with the train, it must cover the 100 miles difference at the rate of 20mi/hr. So the time it would need to cover this difference is
100 / 20 = 5 hours
After 5 hours, the car would have traveled a distance of
5 * 70 = 350 miles which is also the distance from the station to where the car catches up
A contour line connects points of the same elevation. Contour lines are usually curves. Closed contours represent hills.
Contour lines can not cross since they represent different elevations. A contour interval is the difference in elevation between one contour and an adjacent contour.
Displacement is a vector that defines the position of a particle. The vector extends from the initial position to the final position. Therefore, the displacement only takes into account this positions, since its trajectory is not important:
km " ;