Answer Key to Uniform Motion Problems
Involving Current, Headwind, or Moving Sidewalk
1. If the current of the river is 3 mph and Carrie is traveling downstream, her effective
speed is 5 mph + 3 mph = 8mph. Thus, she can travel a distance of 20 miles in
2.5 hours.
2. If it takes the passenger 5 minutes to walk the distance of 600 feet, his walking speed
is
120 feet per minute. The sidewalk moves at a rate of 8 feet per second, or
480 feet per minute. The effective speed of the passenger on the sidewalk
is 120 ft/min + 480 ft/min = 600 feet per minute. It will take him
1 minute to
get to the gate.
3. If the airplane travels 150 miles in 2 hours, his speed in the headwind is
75
miles per hour. This is its normal speed reduced by the speed of the headwind, 30 miles
per hour. Therefore, the airplane’s speed in calm air is 75 mph + 30 mph = 105 miles
per hour.
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