1. A LEVEL PHYSICS Year 1 Vector Components A* A B C
I can add forces at right angles (Grade b)
I can resolve a vector into its two particular components (Grade b/a)

3. To start
Have a go at the exam questions When you’re finished the answers are on the back.

4. To start
Katie is out fishing on the banks of a river when she sees Justin Bieber on the opposite river bank.
She decides it is only right that she swims over to meet him. She swims at a constant velocity of 3 m/s. Unfortunately the river has a current flowing at 5 m/s perpendicular to the direction she wishes to travel.
(Standard) what is her resultant velocity?
(Challenge) at what angle would she have to leave her original position to ensure she meets him?

5. Resolving vectors
The process of working out the two perpendicular components is called resolving. Any vector can be resolved at AS level by following the diagram below: Fr
Fx = Fr cosθ
Fy = Fr sinθ θ

6. Why is this true?

7. A paraglider is pulled along at a constant height and steady speed by a cable attached to a speed boat. The cable pulls on the paraglider with a force of 500N at an angle of 35o to the horizontal. Calculate the horizontal and vertical components of this force.
Always draw force diagrams clearly (big), representing magnitude and direction as accurately as possible Fy
500N
35o Fx
Fx = 500 cos 35 = 410N horizontally
Fy = 500 sin 35 = 290N vertically

8. Resolving vectors on a slope
(or inclined plane)
Resolving forces on a slope is very useful and will crop up a lot in mechanics. The two perpendicular components of a vector do not affect each other. This means you can deal with the two directions completely separately (when a force only affects one vector you can ignore the other).
Weight always acts vertically down (towards the centre of the earth)

10. Practice makes perfect!
Standard
Complete Practice Questions 1 to 4 on page 114.
Follow the first one on the board as I work through it, making notes of the steps, then complete the rest yourself.
Mark your answers, make sure you clarify any mistakes with me.
Challenge
Complete Practice Questions 1 to 4 on page 114.
Mark your answers, make sure you clarify any mistakes with me.
Complete the questions below:
Q.1 A postal employee drives a delivery truck over the route shown in the diagram. Use the method of components to determine the magnitude and direction of her resultant displacement.
Q.2 A spelunker is surveying a cave. She follows a passage 180m straight west, the 210m in a direction 45 degrees east of south, and then 280m at 30 degrees east of North. After a fourth unmeasured displacement, she finds herself back where she started, Use a scale drawing to determine the magnitude and direction of the fourth displacement.

11. Exam Question Homework Sheet

12. Next Lesson: Resolving vectors into their components
Lesson after that: Forces in equilibrium