An object has rest mass $m$. If the object's relativistic momentum is $4 m c$, then its speed must be $4 c$.

Francois is travelling at a speed of $0.95 \mathrm{c}$ on a railway car, which Francois has measured as $25 \mathrm{~m}$ in length. Soledad, who is located on the ground near the railway tracks, arranges for two small explosions to occur on the ground next to the ends of the railway car. According to Soledad, the two explosions occur simultaneously, and she uses the burn marks on the ground to measure the length of Francois's railway car. According to Francois, do the two explosions occur simultaneously? If not, then according to Francois, which explosion occurs first?

A person is in a railway car without any windows. What test can the person perform to determine whether the car is at rest or is moving at constant velocity? (a) toss a ball horizontally (b) drop a ball vertically (c) let two masses collide on the floor (d) There is no experiment the person can do to determine whether the car is at rest or moving at constant velocity.

A process takes place in a given amount of time. (a) Does the process seem to take longer for an observer moving relative to the process, or for an observer at rest with respect to the process? (b) Which observer measures the proper time of the process?

Consider the properties of inertial and non-inertial frames of reference. (a) How does an inertial frame of reference differ from a non-inertial frame of reference? (b) Give two examples of each type of frame of reference.

The mass of a particle travelling at nearly the speed of light increases beyond its rest mass.

Einstein originally wanted to call his model "the special theory of reference frames.

As an object moves at a speed close to the speed of light, length measured in the direction of the speed contracts.

Only electrons can be accelerated to speeds faster than the speed of light.

Calculations using global positioning satellites need to account for relativistic effects, such as time dilation.

The equation for time dilation predicts that to bring about relativistic effects, objects must be moving faster than the speed of light.

Given a stationary observer and an observer who is moving near the speed of light, time will pass slower for the stationary observer.

As straight water waves pass through an opening and spread out in circular wave fronts, the waves undergo (a) reflection (b) refraction (c) dispersion (d) diffraction

For any process, the dilated time will always be less than the proper time.