Question

You are on a train traveling east at speed of 28 m/s with respect to the ground. 1) If you walk east toward the front of the train, with a speed of 1.5 m/s with respect to the train, what is your velocity with respect to the ground? (m/s east)

2) If you walk west toward the back of the train, with a speed of 2.1 m/s with respect to the train, what is your velocity with respect to the ground? (m/s, east)
3) Your friend is sitting on another train traveling west at 22 m/s. As you walk toward the back of your train at 2.1 m/s, what is your velocity with respect to your friend? (m/s, east)

Answer 1

A) 29.5m/s

B) 25.9m/s

C) 47.9 m/s

Step-by-step explanation:

This is a relative velocity problem, which means that the velocity perception will vary from each observer at a different reference point.

We can say that the velocity of the train respect the ground is 28m/s on east direction If I walk 1.5m/s respect the train, the velocity of the person respect to the ground is the sum of both velocities:

Vgp=Vgt+Vtp

where:

Vgp=velocity of the person respect the ground

Vgt=Velocity of the train respect the ground

Vtp=Velocity of the person respect the train

1) Vgp=28m/s+1.5m/s=29.5m/s

2) here the velocity of the person respect the train is negative because it is going backward

Vgp=28m/s-2.1m/s=25.9m/s

3) the velocity of the train respect with your friend will be the sum of both velocities(Vft).

Vfp=Vft+Vtp

Vfp=velocity of the person respect the friend

Vft=Velocity of the train respect the friend

Vtp=Velocity of the person respect the friend

Vfp=(22m/s+28m/s)+(-2.1m/s)=47.9 m/s