How did Einstein reconcile the idea that motion is relative with the observation that the speed of light $c$ is constant in all inertial frames?

At what speed, as a fraction of c, is the kinetic energy of a particle twice its Newtonian value?

The sun radiates energy at the rate 3.8 x 10²⁶ W. The source of this energy is fusion, a nuclear reaction in which mass is transformed into energy. The mass of the sun is 2.0 x 10³⁰ kg. What percent is this of the sun's total mass?

The sun radiates energy at the rate 3.8 x 10²⁶ W. The source of this energy is fusion, a nuclear reaction in which mass is transformed into energy. The mass of the sun is 2.0 x 10³⁰ kg. Fusion takes place in the core of a star, where the temperature and pressure are highest. A star like the sun can sustain fusion until it has transformed about 0.10% of its total mass into energy, then fusion ceases and the star slowly dies. Estimate the sun's lifetime, giving your answer in billions of years.

Which of the following statements is true concerning special relativity?

You are a passenger on a spaceship. As the speed of the spaceship increases and approaches the speed of light, which of the following effects would you observe according to special relativity?

Suppose there is an astronaut who is traveling at a significant fraction of the speed of light $c$ relative to Earth. According to special relativity, which of the following effects would the astronaut experience compared to an observer at rest on Earth?

Suppose the two lightning bolts shown in Fig. 37.5a are simultaneous to an observer on the train. Show that they are not simultaneous to an observer on the ground. Which lightning strike does the ground observer measure to come first?