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1. What is the fastest motion that can be measured in any frame of reference?

A. 300,000 m/s
B. 186,000 m/s
C. 186,000 km/s
D. 300,000 km/s

2. Two people are on a train that is moving at 10 m/s north. They are walking 1 m/s south relative to the train. Relative to the ground, their motion is 9 m/s north.

Why are we able to use these motions to describe the motion relative to the ground?

A. If one point is moving much slower tjan the speed of light, its speed can be added to that of another object.
B. The motion of everything in the Universe besides light can be described in this way.
C. As long as the frame of reference is stationary, all motion can be described in this way.
D. The people are moving much slower than the speed of light so the ground acts as a frame of reference.

1 answer

  1. The fastest motion that can be measured in any frame of reference is:

D. 300,000 km/s

This is the speed of light in a vacuum, often approximated as 299,792 km/s or about 300,000 km/s. Light travels at this speed regardless of the observer's frame of reference.

  1. The reason we are able to use these motions to describe the motion relative to the ground is:

D. The people are moving much slower than the speed of light so the ground acts as a frame of reference.

In classical mechanics, when objects are moving at speeds much lower than the speed of light, velocities can be added linearly to find the resultant speed relative to a different frame of reference (in this case, the ground).