Answer:
a. boat would drift towards a NE direction
b. 104.4m/min * t
c. false
d. point downstream of c, -79.19 deg NE
e. 3.898mins
f. 389.8m
Explanation:
a. downstream is a location with respect to the direction of the flow of the river, in this case from west to east. the boat would drift towards the NE direction due to the direction of water current.
b. lets say it takes time t to travel across the river, the resultant speed of boat would be given as Rs= sqrt ( 100/min^2 + 30m/mins^2) = 104.4m/mins
distance traveled would be 104.4 *t
c. false, the direction of boat wouldnt remain perpendicular the entire crossing but would drift toward the NE bearing provided the driver doesnt change or steer the boat.
d. a. taking the definition of downstream in question (a), your boat would land at a point x downstream to c
b. to land at c boat must be inclined at an angle of -79.19 deg NE, given by using the width of river and the distance of b to c.
cosФ= 75/ 400
Ф= 79.19°NE to get to c you must position boat at an angle of -79.19 deg from your initial bearing.
e. speed = distance/ time, time = distance / speed.
aiming toward point c, speed of boat is the resultant speed of boat with respect to the speed of water, using Pythagoras also
speed= = 104m/mins
distance to move from point a to c is given also given by
distance = = 406.97m
time = 406.97/ 104.4 = 3.89mins...
f. on the ground the observer see the boat speed as 100m/min.
distance traveled is given by speed * time= 100 * 3.89= 389m
g. speed of boat observed would be 100m/min