The speed of light and relativity
Grade 11 Science Worksheet

Circle the best answer, or write your answer on the line.
A muon at rest lives 2.197 μs on average (PDG). Measured from the ground, how long does one moving at 0.995c last, to 0.01 μs, Bo?
A muon at rest lives 2.197 μs on average (PDG). Measured from the ground, how long does one moving at 0.98c last, to 0.01 μs, Esme?
Read this first
GPS satellite clocks compared with ground clocks (from Ashby's fractional rates × 86,400 s)
Effect Change in the satellite clock (μs per day) Weaker gravity at its height +45.7 Its orbital speed -7.1 Net +38.6 Using the table, does a GPS satellite clock run fast or slow overall, compared with ground clocks, Jun?
- Slow, by about 38.6 μs a day
- The two effects cancel exactly
- Fast, by about 38.6 μs a day
Using the table, why does the satellite's speed make its clock lose time, Kira?
- Its batteries run down
- Moving clocks tick slower
- Space is colder than the ground
Using the table, why does the satellite's height make its clock gain time, Luz?
- Its speed makes it run fast
- It is closer to the Sun
- Gravity is weaker up there
A rod moves past at 0.8c. Measured from the ground, how long is it along its motion, Milo?
- Longer than at rest
- Shorter than at rest
- Exactly as long as at rest
Muons made high in the air reach the ground in large numbers. Why, Noah?
- They travel faster than light
- Their lifetimes are stretched
- Air makes them live longer
Two matched clocks: one rides a fast rocket and returns, one stays put. Ignoring gravity, which shows less time, Pia?
- They show the same time
- The one that rode the rocket
- The one that stayed put
As an object gets close to c, what happens to the energy needed to speed it up more, Ren?
- It stays the same
- It drops to zero
- It grows without limit
Sunlight takes about 499 seconds to reach Earth. What does this show, Zee?
- Sunlight slows down in space
- Light's speed is finite
- Light arrives instantly

