Relative Motion

Question 1

Train Alpha and Train Beta travel side‑by‑side on parallel tracks heading north. Both trains travel at exactly 90 km/h. A passenger on Train Alpha looks out the window at Train Beta. Which explanation best describes why the passenger sees Train Beta as not moving?

Accepted Answer

Because the passenger shares the same forward motion as Train Alpha, Train Beta has a velocity of 0 km/h relative to the passenger, so it appears stationary.

Answer

Because Train Beta is moving at 90 km/h relative to the ground, the passenger will also see it moving at 90 km/h.

Answer

Since the passenger is already moving, the speeds add, so the passenger sees Train Beta moving at 180 km/h.

Answer

The wind created by both trains blows at the same speed, making Train Beta invisible to the passenger.

Question 2

A train is traveling east at 60 km/h and a car is traveling west at 40 km/h on parallel tracks. How fast are the train and the car moving relative to each other?

Accepted Answer

100 km/h

Answer

20 km/h

Answer

60 km/h

Answer

40 km/h

Question 3

Train Aurora travels east at 65 km/h on Track 1. Train Borealis travels east on the adjacent Track 2 at exactly the same speed, 65 km/h. Maya is seated inside Train Aurora and looks out the window at Train Borealis. Which statement best explains why Maya perceives Train Borealis as not moving, even though a person standing on the platform sees both trains moving east at 65 km/h?

Accepted Answer

Because Maya and Train Borealis share the same eastward speed, their relative speed is zero, so from Maya’s frame of reference Borealis does not change its position.

Answer

Because Maya is inside a moving train, her eyes cannot detect any motion of objects outside the train.

Answer

Because the two trains are on separate tracks, they cannot affect each other’s motion, making them appear stationary to each other.

Answer

Because the distance between the trains stays constant, the platform’s speed measurement does not apply to what Maya sees.

Try three questions

Train Alpha and Train Beta travel side‑by‑side on parallel tracks heading north. Both trains travel at exactly 90 km/h. A passenger on Train Alpha looks out the window at Train Beta. Which explanation best describes why the passenger sees Train Beta as not moving?

A train is traveling east at 60 km/h and a car is traveling west at 40 km/h on parallel tracks. How fast are the train and the car moving relative to each other?

Keep going on this shelf