Ch 2 Physics Class 11 Notes

• Differentiate between scalars and vectors.
• How a vector is represented?
• What is rectangular coordinate system? Discuss its two types.
• What is head to tail rule?: Ans: Ans: It is a graphical method used for the addition of the forces. Explanation: - • First draw all forces according to suitable scale such as A and B. • Take one of the forces as a first vector. For example, vector A. • Then draw the next vector B such as its tail coincides with the head of the first vector. • Similarly draw the all-next forces (if any) with its tail coinciding with the head of the previous force and so on. • Now draw a vector R such that its tail is at the tail of vector A, the first vector, while its head is at the head of vector B, the last vector.
• How a vector is subtracted?
• Discuss multiplication of a vector: Ans: Multiplication of a vector by a scalar: A vector can be multiplied by: • A positive number. • A negative number. • A scalar with dimension. (i) Multiplication with a positive number: When a vector A  is multiplied by a positive number n (n > 0) then the product vector will have magnitude equal to nA and same direction as that of A  . (ii) Multiplication with a negative number: When a vector A  is multiplied by a negative number n (n < 0) then the product vector will have magnitude equal to nA and opposite direction as that of A  . (iii) Multiplication with a scalar quantity: When a vector A  is multiplied by a scalar quantity n. then the product vector will be a new physical quantity whose dimension equal to product of the dimension of n and A  . Examples: • Product of mass and velocity is momentum ( P = mv ) • Product of mass and acceleration is force ( F = ma ) • Product of force and time is impulse ( I = F×t )
• Define resultant vector, unit vector, null vector and equal vector.
• Define rectangular components. Drive its formula.
• Define dot product. Give its two examples.
• Explain four characteristics of dot product.
• Define cross product. Give its two examples.
• Explain right hand rule to find the direction of cross product.
• Explain four characteristics of cross product.
• Prove that area of parallelogram is equal to magnitude of cross product.
• Define torque. Write its formula and unit.
• Define the terms (i) Unit vector (ii) Position Vector and (iii) Component of a Vector. 
• The vector sum of three vectors gives zero resultant. What can be the possible orientation of the vectors?
• If one of the rectangular components of a vector is not zero. Can its magnitude be zero? Explain. 
• Can a vector have components greater than the vector’s magnitude?
• can the magnitude of a vector have a negative value?
• If A+B = 0, What can you say about the components of two vectors? 
• Under what circumstances would a vector have components that are equal in magnitude?
• Is it possible to add a scalar quantity into a vector quantity? Explain.
• can you add zero to a null vector?
• Two vectors have unequal magnitude. Can their sum be equal to zero? Explain. 
• Show that the sum and difference of two perpendicular vectors of equal lengths are also perpendicular and of the same length?
• How would be the two vectors of the same magnitude have to be oriented, if they were to be combined to give the resultant equal to a vector of the same magnitude?
• A picture is suspended from a wall by two strings. Show by diagram the configuration of the strings for which the tension in the string will be minimum. 
• Can a body rotate about its centre of gravity under the action of its weight?