# Physics 114

You are riding in a boat whose speed relative to the water is 7.2 m/s. The boat points at an angle of 25.7° upstream on a river flowing at 14.1 m/s. Find the time it takes for the boat to reach the opposite shore if the river is 24.5 m wide.

1. 👍
2. 👎
3. 👁
1. If we consider the direction across the river as 0deg, then the resultant velocity of the boat is

(angle a is 25.7 deg)

(7.2 cos a, 7.2 sin a) + (0,14.1 sin -90)
= (6.386,3.122) + (0,-14.1)
= (6.386, -10.978)

which is 10.835 in the direction -59.49 deg

So, now we want a course in the same direction, where the x-distance is 24.5

If d is the distance traveled, then 24.5/d = cos -59.45
d = 48.25

48.25/10.835 = 4.45 sec

1. 👍
2. 👎
2. I understand the method you used completely but when I went to enter in the answer it incorrect...any help?

1. 👍
2. 👎

## Similar Questions

1. ### physics

Two people are pulling a boat through the water as in the figure below. Each exerts a force of 600 N directed at a è = 20.0° angle relative to the forward motion of the boat. If the boat moves with constant velocity, find the

2. ### science

a boat heading due north crosses a wide river with speed of 12km/h relative to the water the water in the river has a uniform speed of 5 km/h due east relative to the earth.determine the velocity of the boat relative to an

3. ### cpcc

Two people are pulling a boat through the water as in Figure P4.20. Each exerts a force of 600 N directed at a θ = 45.0° angle relative to the forward motion of the boat. If the boat moves with constant velocity, find the

4. ### Physics

A boat crosses a river of width 122 m in which the current has a uniform speed of 2.39 m/s. The pilot maintains a bearing (i.e., the direction in which the boat points) perpendicular to the river and a throttle setting to give a

1. ### physics

A fisherman sets out upstream from Metaline Falls on the Pend Oreille River in northwestern Washington State. His small boat, powered by an outboard motor, travels at a constant speed v in still water. The water flows at a lower

2. ### physics

A power boat of mass 465 kg is cruising at a constant speed of 8.9 m/s. The propeller provides a drive force of 765 N. The driver of the boat shuts off the engine, and the boat coasts to a halt. Assume-contrary to fact-that the

3. ### Physics

A boat is rowed directly upriver at a speed of 2.4 m/s relative to the water. Viewers on the shore see that the boat is moving at only 0.6 m/s relative to the shore (heading upriver). What is the speed of the river?

4. ### physics - relative motion

A ferryboat, whose speed in still water is 4.00m/s, must cross a river whose current is 3.00m/s. The river runs from west to east and is 128m wide. The boat is pointed north. a) If the boat does not compensate for the flow of the

1. ### math

A boat traveling downstream a distance of 39 miles then came right back.If the speed of the current was 12 mph and the total trip took 4 hours 20 minutes,find the average speed of the boat relative to the water.

2. ### physics

Mary needs to row her boat across a 120 m -wide river that is flowing to the east at a speed of 1.4 m/s. Mary can row the boat with a speed of 2.0 m relative to the water. 1. How long does it take Mary to reach the opposite river

3. ### Physics

A small boat is crossing a river which flows at 10km.h. The driver of the boat keeps it heading directly (at 90) away from the bank at a speed of 24 km/h relative to the water. The river is 0.5 km wide. I calculated the speed of

4. ### math

A boat traveled downstream a distance of 9090 mi and then came right back. If the speed of the current was 88 mph and the total trip took 66 hourscomma nbsp, find the average speed of the boat relative to the water.