Question

boat #1 travels directly across a river from point a to point b, a distance of 100 m, as pictured. the river current moves at a speed of 5 m/s and the boat has a velocity of 2 m/s directly up. how long will it take for boat #1 to cross the river? a 10 sec b 14.3 sec c 20 sec d 50 sec

Explanation:

Step1: Recall the formula for time

The formula for time \( t=\frac{d}{v} \), where \( d \) is the distance and \( v \) is the velocity. In the direction perpendicular to the river - bank (the direction we care about for crossing the river), the velocity of the boat is \( v = 2m/s \) and the distance \( d = 100m \).

Step2: Calculate the time

Substitute \( d = 100m \) and \( v=2m/s \) into the formula \( t=\frac{d}{v} \). So, \( t=\frac{100}{2}=50s \).

Answer:

D. 50 sec