1) A train travels with a constant velocity of 100km/h. Another train travels in

Question

1) A train travels with a constant velocity of 100km/h. Another train travels in opposite direction on a parallel track. The speed of the two trains is the same. John is a passenger on the first train and Mary is on the second train. When the train pass by each other...

a) John and Mary are both sitting by the window; they see each other passing by with speed of ...

b) John is walking with speed of 1km/h in the direction of the motion of his train and Mary is walking with the same speed in the opposite direction of the motion of her train; they see each other passing by with speed of...

c) What is the displacement between John to Mary after 1 sec. from when they pass each other if they are sitting?

d) what is the displacement between John to Mary after 1 sec. from when they pass each other if they are walking (as in 2)?

2) Planes fly in a medium of moving air. If the speedometer reads 100 mi/hr, then the plane moves 100 mi/hr relative to the air. But since the air is moving, the plane's speed relative to the ground will be different than 100 mi/hr. Suppose a plane with a 100 mi/hr air speed encounters a tail wind, a head wind and a side wind of 25 mi/hr. Determine the resulting speed of the plane relative to the Earth and the displacement of the plane (still relative to the Earth) after 1 hr for each situation.

In this problem you do not need to use the explicit value for "c": solve the problem using the letter "c" wherever it is applicable.

Explanation / Answer

ans 1

part a

vt/g = 100 Km/h

so relative velocicty if both trevelling in different direction

vjohn/ground =100Km/H

Vmarry/ground =-100Km/h

Vjohn/marry = 100-(-100) =200Km/h

part b

speed of john with repsect to ground =100+1 =101Km/h

speed of marry with repsect to ground=100-1=99Km/h opposite of john direction

so both will be add so passing speed=101+99=200km/h

part c

displacement after 1 sec

distance=speed*time=200*1/60*60 =0.05555km=55.555m

part d

distance =200*1/60*60=0.055555km=55.555m

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