A movie stunt double is supposed to run across the top of a train (in the opposite direction that the train is moving) and just barely jump off before reaching a tunnel, but after running the entire length of the train (starting from the front). If the train is moving at 50 km/hr, is 3 km long and the tunnel is 40 km away from the end (where the stunt double is going to jump from), how fast (in km/hr) will the stunt double need to run

3.49km/hr

Explanation:

This train is moving at 50km/hr

Distance = length of train + distance of tunnel

= 3 km + 40 km

= 43 km

Time taken by train to get to tunnel

Time = distance / velocity

Time = 43 km/50km perhour

= 0.86

How fast will stunt double have to run?

Velocity = 3km/0.86

= 3.49 km/hr

The stunt double will have to run as fast as 3.49 kilometer per hour

- measure reactants precisely. ( first choice)

- stir to the reaction take place. ( second choice)

- wait patiently until the reaction completes. ( fourth choice)

- make sure to recover as much copper as possible. ( last choice)