Mark the correct statements about the friction between two bodies.
(a) | static friction is always greater than kinetic friction. |
(b) | coefficient of static friction is always greater than the coefficient of kinetic friction. |
(c) | limiting friction is always greater than kinetic friction. |
(d) | limiting friction is never less than static friction. |
Choose the correct option:
1. | (a), (b) and (c) |
2. | (b), (c) and (d) |
3. | (a) and (d) |
4. | (c) and (d) |
In the figure, the coefficient of friction between the floor and body \(B\) is \(0.1.\) The coefficient of friction between bodies \(B\) and \(A\) is \(0.2.\) A force \(F\) is applied as shown on \(B.\) The mass of \(A\) is \(rn/2\) and of \(B\) is \(m.\)
(a) | The bodies will move together if \(F = 0.25\text{mg}\) |
(b) | The \(A\) will slip with \(B\) if \(F = 0.5\text{mg}\) |
(c) | The bodies will move together if \(F = 0.5\text{mg}\) |
(d) | The bodies will be at rest if \(F = 0.1\text{mg}\) |
(e) | The maximum value of \(F\) for which the two bodies will move together is \(0.45\text{mg}\) |
Which of the following statement(s) is/are true?
1. (a), (b), (d), (e)
2. (a), (c), (d), (e)
3. (b), (c), (d)
4. (a), (b), (c)
Assertion (A): | Angle of repose is equal to the angle of limiting friction. |
Reason (R): | When a body is just at the point of motion, the force of friction at this stage is called limiting friction. |
1. | Both (A) and (R) are true and (R) is the correct explanation of (A). |
2. | Both (A) and (R) are true but (R) is not the correct explanation of (A). |
3. | (A) is true but (R) is false. |
4. | (A) is false but (R) is true. |
Assertion (A): | The acceleration of a body down a rough inclined plane is greater than the acceleration due to gravity. |
Reason (R): | The body is able to slide on an inclined plane only when its acceleration is greater than the acceleration due to gravity. |
1. | Both (A) and (R) are true and (R) is the correct explanation of (A). |
2. | Both (A) and (R) are true but (R) is not the correct explanation of (A). |
3. | (A) is true but (R) is false. |
4. | Both (A) and (R) are false. |
Assertion (A): | It is easier to pull a heavy object than to push it on a levelled ground. |
Reason (R): | The magnitude of the frictional force depends on the nature of the two surfaces in contact. |
1. | Both (A) and (R) are True and (R) is the correct explanation of (A). |
2. | Both (A) and (R) are True but (R) is not the correct explanation of (A). |
3. | (A) is True but (R) is False. |
4. | Both (A) and (R) are False. |
Assertion (A): | The use of ball bearings between two moving parts of a machine is a common practice. |
Reason (R): | Ball bearings reduce vibrations and provide good stability. |
1. | Both (A) and (R) are true and (R) is the correct explanation of (A). |
2. | Both (A) and (R) are true but (R) is not the correct explanation of (A). |
3. | (A) is true but (R) is false. |
4. | Both (A) and (R) are false. |
Assertion (A): | It is difficult to move a bicycle along a road with its brakes on. |
Reason (R): | When a bicycle moves with its brakes on, it skids and sliding friction is greater than rolling friction. |
1. | Both (A) and (R) are True and (R) is the correct explanation of (A). |
2. | Both (A) and (R) are True but (R) is not the correct explanation of (A). |
3. | (A) is True but (R) is False. |
4. | Both (A) and (R) are False. |