Question
A train travels west at a rate of 60 kilometers per hour (km/hr) relative to the ground. The train appears to be traveling east at a rate of 10 km/hr to the driver of a car.
image.png
What is the motion of the car relative to the ground?
West and slower than the train
East and slower than the train
East and faster than the train
West and faster than the train
image.png
What is the motion of the car relative to the ground?
West and slower than the train
East and slower than the train
East and faster than the train
West and faster than the train
Answers
GPT-5 mini
Let east be positive. Then
v_train/ground = −60 km/h (west),
v_train/car = +10 km/h (east).
Relative velocity formula: v_train/car = v_train/ground − v_car/ground.
So 10 = −60 − v_car → v_car = −70 km/h.
Thus the car is moving west at 70 km/h — west and faster than the train.
v_train/ground = −60 km/h (west),
v_train/car = +10 km/h (east).
Relative velocity formula: v_train/car = v_train/ground − v_car/ground.
So 10 = −60 − v_car → v_car = −70 km/h.
Thus the car is moving west at 70 km/h — west and faster than the train.