2.6 EXERCISES
1. A particle undergoes three successive displacements in a plane as follows; 4.0 metres southeast. 5.0 metres east and 6.0 metres in a direction \( 60^{\circ} \) North of East. Find the magnitude and direction of the resultant displacement.
2. Given that \( \vec{F}_{1}=3 \hat{i}+4 \hat{j}+5 \hat{k}, \vec{F}_{2}=2 \hat{i}+3 \hat{k} \) and \( \vec{F}_{3}=6 \hat{i}-7 \hat{j}-8 \hat{k} \). Find \( 3 \overrightarrow{\mathrm{~F}}_{1}+2 \overrightarrow{\mathrm{~F}}_{2}+3 \overrightarrow{\mathrm{~F}}_{3} \).
3. A car driver traveling northeast at \( 11.5 \mathrm{~ms}^{-1} \) notices that the wind appears to be coming from \( 60^{\circ} \) south of west. Find the velocity of the wind relative to the ground.
4. A person travelling due east at \( 4 \mathrm{~ms}^{-1} \) observes that the wind appears to blow directly from the north. When he doubles his speed the wind appears to come from the northeast. Find the velocity of the wind.
5. Determine the component of the force \( -3 \hat{i}+6 \hat{j}+2 \hat{k} \) in the direction of the vector \( -4 \hat{i}+4 \hat{j}+7 \hat{k} \)
6. For what values a are \( \vec{A}=a \hat{i}-2 \hat{j}+\hat{k} \) and \( \vec{B}=2 a \hat{i}-a \hat{j}+4 \hat{k} \); perpendicular.
7. The angular velocity of a rotating rigid body is \( \vec{\omega}=4 \hat{i}+\hat{j}-2 \hat{k} \). Find the linear velocity of a point \( \mathrm{P}(5,1,3) \) on the body relative to a point \( \mathrm{Q}(3,4,: 2) \) on the axis of rotation.
8. Find the volume of a parallelepiped whose edges are given by \( \vec{A}=2 \hat{i}+3 \hat{j}-\hat{k} \), \( \hat{B}=\hat{i}-2 \hat{j}+2 \hat{k} \) and \( \hat{C}=3 \hat{i}-2 \vec{j}-\hat{k} \).
9. Find the constant, a such that the vectors \( 2 \hat{i}+\hat{j}-\hat{k}, \hat{i}+2 \hat{j}-3 \hat{k} \) and \( 2 \hat{i}+\mathrm{aj}+5 \hat{k} \) are coplanar.
10. Find the area of a triangle with vertices \( (3,-1,2),(1,-1,3) \) and \( (3,-3,1) \).
11. An airplane carrer is steaming at \( 48 \mathrm{~km} / \mathrm{h} \) southeast when a plane takes from its deck and heads in a direction which is \( 15^{\circ} \) west of north. If the speed of the plane is \( 240 \mathrm{~km} / \mathrm{h} \) what will be its displacement relative to the carrier after 2 hours?
12. Determine the resultant of accelerations of \( 18 \mathrm{~ms}^{-2} \) and \( 2.6 \mathrm{~ms}^{-2} \) inclined at an angle of \( 53^{\circ} \), and find its inclination with the smaller acceleration.