Retrieval Practice
Scalars & Vectors — AQA A-Level Physics
Q1. What is the difference between a scalar and a vector?
- A scalar has magnitude only.
- A vector has both magnitude and direction.
Q2. Give three examples of scalar quantities and three examples of vector quantities.
- Scalars: distance, speed, mass (also time, energy, temperature).
- Vectors: displacement, velocity, force (also acceleration, momentum).
Q3. How do you find the resultant of two perpendicular vectors?
Use Pythagoras to find the magnitude (R = sqrt(\(a^{2}\) + \(b^{2}\))) and trigonometry (tan theta = opposite/adjacent) to find the direction.
Q4. What is the triangle method for adding vectors?
- Link the vectors head-to-tail.
- The resultant is the vector from the tail of the first to the head of the second.
Q5. What is the parallelogram method for adding vectors?
Link the vectors tail-to-tail, complete the parallelogram, and the resultant is the diagonal from the common tail.
Q6. How do you resolve a force F at angle theta to the horizontal into components?
- Horizontal component = F cos(theta).
- Vertical component = F sin(theta).
Q7. On an inclined plane at angle theta, what are the components of weight?
- Parallel to slope: W sin(theta).
- Perpendicular to slope: W cos(theta).
Q8. What does it mean for forces to be in equilibrium?
- The resultant force is zero.
- The object is either at rest or moving at constant velocity.
Q9. How do you subtract vectors graphically?
Reverse the direction of the vector being subtracted, then add using the triangle or parallelogram method.
Q10. Why does the cos component always sit adjacent to the angle?
- In a right-angled triangle, cos(theta) = adjacent/hypotenuse.
- The component adjacent to the angle is therefore F cos(theta).