Page 71 - Physics - XI

Q1. The region of the graph where Static friction occurs is from
a. P = 0 N to P = 100 N b. P = 0 N to P = 75 N

c. P = 75 N to P = 100 N d. Only at P = 75 N

Q2. The region of the graph where kinetic friction occurs is
a. P < 50 N b. P < 75 N c. P = 0 N d. P > 75 N

Q3. In an experiment to study the relation between the force of limiting friction and normal
reaction, a body just starts sliding on applying a force of 15 N. What will be the magnitude
of the force of friction acting on the body when the applied forces on it is 3 N?

a. 15 N b. 7.5 N c. 3 N d. 10 N
Q4. In an experiment to study the relation between the force of limiting friction and normal
reaction, a body just starts sliding on applying a force of 15 N. What will be the magnitude

of the force of friction acting on the body when the applied forces on it is 18 N?
a. 15 N b. 7.5 N c. 3 N d. 10 N

Answer key

1. (b), 2. (d), 3. (c), 4. (a)

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) : On a rainy day, it is diffi cult to drive a car or bus at high speed.

Reason(R) : The value of the coeffi cient of friction is lowered due to the wetting of the surface.
2. Assertion(A) : Friction is a necessary evil.

Reason(R) : Though friction dissipates power, but without friction we cannot walk.
3. Assertion(A) : Static friction is a self-adjusting force.

Reason(R) : The coeffi cient of friction does not depend upon the mass of the body.

Answer key
1. (a), 2. (a) , 3. (b)

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