## Practical Exam

Addition of Vectors – Viva Voice Question With Answer

For: Science Class 11 | Physics

**Q.1: What are scalar and vector quantities?**

Ans. (a) Scalar is a physical quantity which is completely represented only by magnitude with a suitable unit, having no direction, e.g. time, mass, speed, density, work, energy, etc.

(b) Vector is a physical quantity has both ‘magnitude and a specified direction’ e.g. displacement, velocity, acceleration, force, weight, torque, momentum, magnetic field intensity, electric field intensity.

**Q.2: Define resolution of vectors?**

Ans. The splitting up of a single vector into two or more vectors is called resolution of vector.

**Q.3: What do you mean by components of a vector?**

Ans. Two or more such vectors which are at right angle to each other are called rectangular components.

**Q.4: What are rectangular component?**

Ans. The components of a vector which are at right angle to each other are called rectangular components.

**Q.5: Define the following: (a) unit vector (b) null vector (c) position vector (d) negative vector**

Ans. (a) Unit vector is that vector whose magnitude is unity ‘1’, and it simply indicates the direction.

(b) Null vector is that vector whose magnitude is zero and it may have any arbitrary direction or no direction. It is also called zero vector.

(c) Position vector is that vector which specifies the position of a point with respect to origin of reference axes.

(d) The negative of a vector is that vector which is equal in magnitude but opposite in direction of that vector.

**Q.6: State head to tail rule of addition of vectors?**

Ans. It states that ‘When the representative lines of all the given are drawn, arrange them in such a way that head of first vector line joins with the tail of second vector, then head of second vector joins with the tail of third vector and so on. The line joining the tail of first vector with head of last vector will represent the resultant vector in magnitude and direction’.

**Q.7: State parallelogram law of vector addition?**

Ans. It states that ‘If two vectors are completely represented by two adjacent sides of a parallelogram, then the diagonal of the parallelogram from the tails of two vectors gives their resultant vector’.

**Q.8: What is a scalar product?**

Ans. When the product of two vectors is a scalar quantity it is called scalar product or dot product, e.g. work is a dot product of force and displacement.

**Q.9: What is a vector product?**

Ans. When the product of two vectors is a vector quantity it is called vector product or cross product, e.g. torque is a vector product of force and force arm.

**Q.10: How a vector is multiply by a number?**

Ans. When a vector is multiplied by a positive number its magnitude changes but direction remains the same. But when a vector is multiplied by a negative number not only its magnitude changes but its direction is also reversed.

**Q.11: What is the unit of force?**

Ans. The force is measured in Newton (MKS system) or in dyne (CGS system) or in pound (BE system).

**Q.12: Define Pythagoras’ theorem.**

Ans. It states that for a right angled triangle: (hypotenuse)^{2 }= (base)^{2} + (perpendicular)^{2}

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