Page 47 - Physics - XI
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Formula for Directions of R:
(sin )
Q
φ = tan 1
PQ
( cos )
Q1. Two forces of magnitude 6 N and 10 N are inclined at an angle of 60° with each other. The
magnitude of the resultant is
a. 16 N b. 14 N c. 4 N d. 12 N
Q2. Given two vectors 8i 3 j k and 16 i 6 j 2k which are parallel, the resultant vector is
a. 24i 9 j 3k b. 8i 3 j k c. 8i 3 j k d. 32i 12 j 5k
Q3. At what angle should the two force vectors 5 N and 12 N be added to get a resultant vector of
13 N?
a. 0° b. 30° c. 90° d. 180°
Q4. If the magnitude of the resultant force of two forces is lesser than the magnitude of the
larger force, then
a. the two forces are perpendicular to each other
b. the two forces are in opposite directions
c. the forces are diff erent in magnitude and direction
d. the forces possess small magnitude
Answer key
1. (b), 2. (a), 3. (c), 4. (b)
Assertion-Reason Type Questions
These consist of two statements– Assertion (A) and Reason (R). Answer these questions by
selecting the appropriate option given below:
a. Both A and R are true and R is the correct explanation of A.
b. Both A and R are true and R is not the correct explanation of A.
c. A is true but R is false.
d. A is false but R is true.
1. Assertion(A) : The sum of two vectors can be zero.
Reason(R) : Two vectors cancel each other when they are equal and opposite.
2. Assertion(A) : A physical quantity cannot be called a vector if it's magnitude is zero.
Reason(R ) : A vector has both magnitude and direction.
Answer key
1. (a), 2. (d)
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