Question

A jetliner is traveling east from Salt Lake City to Washington DC, a distance of 1,850 miles. The jetliner travels at an average air speed of 590 mph relative to the air. At the jetliner's altitude, the wind is blowing 36 mph to the west. How long does the journey take?

Answer 1

21)Velocity of Jetliner relative to air= V Jet - V Air
590= V Jet - (-36)
V Jet = 554mph

Time taken to complete the journey= 1850/554= 3.3 Hours
Option (D) is correct.

22) ( Taking upward direction as positive)

Velocity of Balloon B relative to Balloon A= V b- V a
-12.5= V b - (10)
V b = -2.5 m/s

23)( Taking upward direction as positive)

Velocity of Balloon B relative to Balloon A= V b- V a
7.5= V b - (5)
V b = 12.5 m/s

24) Velocity of car supposedly moving relative to car in which woman was sitting = V a- Vb
0.3= 0 - V b

Velocity of car in which woman was sitting= -0.3 m/sec

Answer 2

21.

Remark

The jet liner is flying against the wind. Therefore the speed of the wind is subtracted from the speed of the aircraft.

Givens

Net Speed = 590 - 36

Net Speed = 554

d = 1850

t = ??

Formula

d = r * t

t = d / r

t = 1850/554

t = 3.34 hours

22

Remark

The person going up is going at + 10. The person going down appears to be going 12.5. The person going up cannot tell what he is doing (or that's what you assume). All he knows for sure is that the second balloon appears to be going down at a rate of 12.5.

In reality, the person on the ground sees what is really happening. His formula is up - appearance to A = down

10 - appearance to A = down

10 - 12.5 = down

- 2.5 = down

23.

You are helped in this question if you understand that B is eventually going to pass A. It won't happen immediately, but it will happen. This question is so much easier if you drive a car. The speed as seen on the ground is the difference between the two balloons. Balloon A is running away from B, just not fast enough.

The ground observer sees what is actually happening. The net velocity is

7.5 - 5.0 = 2.5 if up is the positive direction.

24

This one is actually the worst one of the lot. She thinks she sees the car on her left moving forward. She has no idea what is really happening until she looks to her right.

If you have ever been on a train, you know how tricky this can be. Is the car to her left moving at all? The question does not clarify this unfortunately. Assume it is not. Then it is she that is moving backward.

The answer then is D