Page 59 - Physics - XI

the fi rst extreme position. The time taken by the pendulum to complete one oscillation is called its time
period. The two factors on which time period of a pendulum depends are the length of a string and the
resistance off ered by air.
Q1. Which among the following is an incorrect statement?
a. Increase or decrease in the length of the string will increase or decrease the time period
respectively.
b. The metallic bob is free to swing on the rigid stand.
c. The pendulum is at rest in its extreme positions.

d. The pendulum of a given length always takes the same time to complete one oscillation.
Q2. The simple pendulum is an example of
a. Periodic motion b. Oscillatory motion c. Circular motion d. Both a and b
Q3. Time period is
a. Total time taken/Number of oscillations b. Number of oscillations/Time taken

c. Distance/Time d. Distance/Number of oscillations
Q4. One oscillation is completed when the bob of the pendulum moves from
a. one extreme to the other
b. one extreme to the other and back to the fi rst extreme position
c. the mean position to one extreme and to the other extreme
d. the extreme to its mean position

Answer key
1. (c), 2. (d), 3. (a), 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) : When a pendulum moves to-and-fro from its fi xed position, it is said to complete
one oscillation.
Reason(R) : Time period is the time taken by a pendulum to complete one oscillation.

2. Assertion(A) : Time period of a simple pendulum does not depend on the mass of the bob.
Reason(R ) : The restoring force is independent of the mass of the bob.

3. Assertion(A) : The time period of a simple pendulum is independent of its length.

Reason(R ) : The length of a pendulum is the distance between the point of suspension and
centre of the bob.
Answer key

1. (b), 2. (c) , 3. (d)

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