1. On May 26, 1934, a streamlined, stainless steel diesel train called the Zephyr set the world's nonstop long-distance speed record for trains. Its run from Denver to Chicago took 13 hours, 4 minutes, 58 seconds, and was witnessed by more than a million people along the route. The total distance traveled was 1633.8 km. What was its average speed in km/h?

2. The speed of propagation of the action potential (an electrical signal) in a nerve cell depends (inversely) on the diameter of the axon (nerve fiber). If the nerve cell connecting the spinal cord to your feet is 0.8 m long, and the nerve impulse speed is 20 m/s, how long (in s) does it take for the nerve signal to travel this distance?

3. Nerve impulses in the human body travel at a speed of about 100 m/s. A 1.9 m tall man accidentally drops a hammer on his toe. How long does it take for the nerve impulse to travel from his toe to his brain?