Interception: find bearing/direction to intercept (exact intercept)

4. A rescue boat, whose maximum speed is \(20 \mathrm {~km} \mathrm {~h} ^ { - 1 }\), receives a signal which indicates that a yacht is in distress near a fixed point \(P\). The rescue boat is 15 km south-west of \(P\). There is a constant current of \(5 \mathrm {~km} \mathrm {~h} ^ { - 1 }\) flowing uniformly from west to east. The rescue boat sets the course needed to get to \(P\) as quickly as possible. Find

1. the course the rescue boat sets,
2. the time, to the nearest minute, to get to \(P\). When the rescue boat arrives at \(P\), the yacht is just visible 4 km due north of \(P\) and is drifting with the current. Find
3. the course that the rescue boat should set to get to the yacht as quickly as possible,
4. the time taken by the rescue boat to reach the yacht from \(P\).

3 From a speedboat, a ship is sighted on a bearing of \(045 ^ { \circ }\). The ship has constant velocity \(8 \mathrm {~m} \mathrm {~s} ^ { - 1 }\) in the direction with bearing \(120 ^ { \circ }\). The speedboat travels in a straight line with constant speed \(15 \mathrm {~m} \mathrm {~s} ^ { - 1 }\) and intercepts the ship.

1. Find the bearing of the course of the speedboat.
2. Find the magnitude of the velocity of the ship relative to the speedboat.

1 Alan is running in a straight line on a bearing of \(090 ^ { \circ }\) at a constant speed of \(4 \mathrm {~ms} ^ { - 1 }\). Ben sees Alan when they are 50 m apart and Alan is on a bearing of \(060 ^ { \circ }\) from Ben. Ben sets off immediately to intercept Alan by running at a constant speed of \(6 \mathrm {~m} \mathrm {~s} ^ { - 1 }\).

1. Calculate the bearing on which Ben should run to intercept Alan.
2. Calculate the magnitude of the velocity of Ben relative to Alan and find the time it takes, from the moment Ben sees Alan, for Ben to intercept Alan.

2 A ship \(S\) is travelling with constant speed \(5 \mathrm {~ms} ^ { - 1 }\) on a course with bearing \(325 ^ { \circ }\). A second ship \(T\) observes \(S\) when \(S\) is 9500 m from \(T\) on a bearing of \(060 ^ { \circ }\) from \(T\). Ship \(T\) sets off in pursuit, travelling with constant speed \(8.5 \mathrm {~ms} ^ { - 1 }\) in a straight line.

1. Find the bearing of the course which \(T\) should take in order to intercept \(S\).
2. Find the distance travelled by \(S\) from the moment that \(T\) sets off in pursuit until the point of interception.

3 A fishing boat is travelling between two ports, \(A\) and \(B\), on the shore of a lake. The bearing of \(B\) from \(A\) is \(130 ^ { \circ }\). The fishing boat leaves \(A\) and travels directly towards \(B\) with speed \(2 \mathrm {~m} \mathrm {~s} ^ { - 1 }\). A patrol boat on the lake is travelling with speed \(4 \mathrm {~ms} ^ { - 1 }\) on a bearing of \(040 ^ { \circ }\). \includegraphics[max width=\textwidth, alt={}, center]{719b82f7-2ab5-48db-9b2a-98284096a78a-3_713_1319_443_406}

1. Find the velocity of the fishing boat relative to the patrol boat, giving your answer as a speed together with a bearing.
2. When the patrol boat is 1500 m due west of the fishing boat, it changes direction in order to intercept the fishing boat in the shortest possible time.
   1. Find the bearing on which the patrol boat should travel in order to intercept the fishing boat.
   2. Given that the patrol boat intercepts the fishing boat before it reaches \(B\), find the time, in seconds, that it takes the patrol boat to intercept the fishing boat after changing direction.
   3. State a modelling assumption necessary for answering this question, other than the boats being particles.

8 \includegraphics[max width=\textwidth, alt={}, center]{d8ca5464-435f-45e0-8e19-1830415a7c60-4_757_729_260_708} An aircraft carrier, \(A\), is heading due north at \(40 \mathrm {~km} \mathrm {~h} ^ { - 1 }\). A destroyer, \(D\), which is 8 km south-west of \(A\), is ordered to take up a position 3 km east of \(A\) as quickly as possible. The speed of \(D\) is \(60 \mathrm {~km} \mathrm {~h} ^ { - 1 }\) (see diagram). Find the bearing, \(\theta\), of the course that \(D\) should take, giving your answer to the nearest degree.

A pilot flying an aircraft at a constant speed of 2000 kmh\(^{-1}\) detects an enemy aircraft 100 km away on a bearing of 045°. The enemy aircraft is flying at a constant velocity of 1500 kmh\(^{-1}\) due west. Find

1. the course, as a bearing to the nearest degree, that the pilot should set up in order to intercept the enemy aircraft,
2. the time, to the nearest s, that the pilot will take to reach the enemy aircraft. [11]

A boy enters a large horizontal field and sees a friend 100 m due north. The friend is walking in an easterly direction at a constant speed of 0.75 m s\(^{-1}\). The boy can walk at a maximum speed of 1 m s\(^{-1}\). Find the shortest time for the boy to intercept his friend and the bearing on which he must travel to achieve this. [6]

At noon, a boat \(P\) is on a bearing of \(120°\) from boat \(Q\). Boat \(P\) is moving due east at a constant speed of \(12\) km h\(^{-1}\). Boat \(Q\) is moving in a straight line with a constant speed of \(15\) km h\(^{-1}\) on a course to intercept \(P\). Find the direction of motion of \(Q\), giving your answer as a bearing. [5]

At noon two ships \(A\) and \(B\) are 20 km apart with \(A\) on a bearing of 230° from \(B\). Ship \(B\) is moving at 6 km h\(^{-1}\) on a bearing of 015°. The maximum speed of \(A\) is 12 km h\(^{-1}\). Ship \(A\) sets a course to intercept \(B\) as soon as possible.

1. Find the course set by \(A\), giving your answer as a bearing to the nearest degree. [4]
2. Find the time at which \(A\) intercepts \(B\). [4]