Final answer:
Watson needs to jump at a minimum speed of 3.5 meters/second to cover a distance of 7 meters across a ravine in 2 seconds, with the correct answer being option B.
Step-by-step explanation:
To calculate the minimum speed with which Watson, a mountaineer, should attempt to jump over a ravine that is 7 meters wide to escape an approaching avalanche, we ignore vertical motion and focus on the horizontal motion. Since Watson attempts to clear the ravine in 2 seconds, we can use the following formula for constant speed in horizontal direction:
speed = distance/time.
The distance Watson needs to cover is 7 meters, and he has 2 seconds to make the jump. Hence, Watson's minimum speed should be:
minimum speed = distance/time = 7 meters / 2 seconds = 3.5 meters/second.
The correct answer is B. 3.5 meters/second, which is the minimum speed Watson must have to safely reach the other side of the ravine.