Conceptual Questions Based on Class 11 Physics Vectors

Here we are providing conceptual questions for class 11 physics vectors. Answers are also provided along with questions. So that students can read and understand the question. These questions are prepared by the subject experts. Students can read these conceptual questions based on vectors for better topic clarity and will be able to score better marks in their exam.

Conceptual Questions Based on Class 11 Physics Vectors

Question 1. Why cannot be vectors added algebraically?

Solution. Apart from magnitude, the vectors also have directions, so they cannot be added algebraically.

Question 2. Is time a vector quantity? Give reason.

Solution. No. Time flows from past to present and present to future. Thus, the direction of time flow is unique and does not need to be specified. Hence time is not a vector, though it has a direction.

Question 3. Under what condition will the directions of sum and difference of two vectors be same?

Solution. When the two vectors are unequal in magnitude and are in the same direction.

Question 4. State the essential condition for the addition of vectors.

Solution. The essential condition for the addition of vectors is that they must represent the physical quantities of same nature.

Question 5. Can two vectors of different magnitudes be combined to give zero resultant?

Solution. No, two vectors of different magnitudes cannot be combined to give zero resultant.

Question 6. Can we add a velocity vector to a displacement vector?

Solution. No, only vectors representing physical quantities of same nature can be added together.

Question 7. Is pressure a vector? Give reason.

Solution. No. Pressure is always taken to be normal to the plane of the area on which it is acting. As this direction is unique, it does need any specification. So, pressure is not a vector.

Question 8. When is the magnitude of the resultant of two vectors equal to either of them?

Solution. When two vectors of equal magnitude are inclined to each other at an angle of 120°, the magnitude of their resultant is equal to that of the either vector.

a² = a² + a² + 2a² cos² θ

⇒ cos θ = – 1/2 ⇒ θ = 120°

Question 9. What is the vector sum of n coplanar forces, each of magnitude F, if each force makes an angle of 2π/n with the preceding force?

Solution. Total angle between n coplanar forces = (2π/n) × n = 2π. This shows that the n forces can be represented by the n sides of a closed polygon taken in the same order. So, the resultant force is zero.

Question 10. What is the minimum number of coplanar vectors of different magnitudes which can give zero resultant?

Solution. Three. If three vectors can be represented by the three sides of a triangle taken in the same order, then their resultant is a zero vector.

Question 11. Can a vector be multiplied by both dimensional and non-dimensional scalars?

Solution. Yes. When a vector is multiplied by a dimensional scalar, the resultant has different dimensions. When the vector is multiplied by a non-dimensional scalar, its dimensions remain unchanged.

Question 12. Is finite rotation a vector?

Solution. No. This is because the addition of two finite rotations about different axes does not obey commutative law.

Question 13. What is the maximum number of components into which a vector can be resolved?

Solution. Infinite.

Question 14. Give two conditions necessary for a given quantity to be a vector.

Solution. (i) The quantity must have both magnitude and direction.

(ii) It must obey the laws of vector addition.

Question 15. Can the scalar product of two vectors be negative?

Solution. Yes, the scalar product is negative when the angle between two vectors lies between 90° and 270°.

Question 16. What is the dot product of two dissimilar unit vectors?

Solution. Zero.

Question 17. Two persons are pulling the ends of a string in such a way that the string is stretched horizontally. When a weight of 10 kg is suspended in the middle of the string, the string does not remain horizontal. Can the persons make it horizontal again by putting it with a greater force?

Solution. No, the vertical weight cannot be balanced by the horizontal force, however large the two forces may be.

Question 18. What is the condition for two vectors to be collinear?

Solution. For two given vectors to be collinear, their cross-product must be zero.

Question 19. Read each statement below carefully and state with reasons, if it is true or false:

(a)   The magnitude of a vector is always a scalar.

(b)   Each component of a vector is always a scalar.

(c)   The total path length is always equal to the magnitude of the displacement vector of a particle.

(d)   The average speed of a particle (defined as total path length divided by the time taken to cover the path) is either greater or equal to the magnitude of average velocity of the particle over the same interval of time.

(e)   Three vectors not lying in a plane can never add up to give a null vector.

Solution. (a) True. The magnitude of a vector is a pure number and has no direction.

(b)   False. Each component of a vector is also a vector.

(c)   False. The displacement depends only on the end points while the path length depends on the actual path. The two quantities are equal only if the direction of motion of the object does not change. In all other cases, path length is greater than the magnitude of displacement.

(d)   True. This is because the total path length is either greater than or equal to the magnitude of displacement over the same interval of time.

(e)   True. This is because the resultant of two vectors will not lie in the plane of third vector and hence cannot cancel its effect to give null vector.

---

Conceptual Questions Based on Class 11 Physics

You May Also Like:

Category Lists (All Posts)

Download CBSE Books