Using four vectors, show that it is impossible to have an inertial reference frame in which a photon is motionless.

Laboratory experiments, observational field studies, and model-building are all examples of different forms of scientific investigations.  in what way do laboratory experiments primarily differ from other forms of scientific investigations?   a.  a laboratory experiment is the only accepted form of investigation within the scientific community.  b.  studies about how things behave in nature or studies involving very large objects are best answered through laboratory experiments.  c.  laboratory experiments involve the identification and control of variables.  d.  data can only be generated through laboratory experiments, not other forms of investigation.

Zeros that follow non-zeros numbers and are also to the right of a decimal point are significant

What is the average speed of a car that travels 40 mph for 1 hour and 60 mph in another hour?