If a body is lying on a plane whose inclination with the horizontal is less than the angle of friction, then i. a force is required to move the body upwards ii. a force is required to move the body downward iii. the body will not be in equilibrium The correct answer is

If a body is lying on a plane whose inclination with the horizontal is less than the angle of friction, then
i. a force is required to move the body upwards
ii. a force is required to move the body downward
iii. the body will not be in equilibrium
The correct answer is

A

only (i)

B

only (ii)

C

both (i) and (ii)

D

both (i) and (iii)

Which of the following is NOT true about Frictional force? A. Friction is the force which opposes the relative motion of two surfaces in contact. B. The force of friction that acts when a body is moving (sliding) on a surface is called sliding friction. C. Friction in machines wastes energy and also causes wear and tear. D. Rolling friction is much more than sliding friction, the use of ball bearings in a machine considerably reduces friction.

A

D

B

A

C

D

B

A body of weight 'W' is required to move up on rough inclined plane whose angle of inclination with the horizontal is 'α'. The effort applied parallel to the plane is given by (where μ = tanφ = Coefficient of friction between the plane and the body.)

A

P = W tanα

B

P = W tan (α + φ)

C

P = W (sinα + μcosα)

D

P = W (cosα + μsinα)

A body of weight W is required to move up the rough inclined plane whose angle of inclination with the horizontal is α. The effort applied parallel to the plane is given by (where $$\mu $$ = $$\tan \varphi $$ = Coefficient of friction between the plane and the body)

A

$${\text{P}} = {\text{W}}\tan \alpha $$

B

$${\text{P}} = {\text{W}}\tan \left( {\alpha + \varphi } \right)$$

C

$${\text{P}} = {\text{W}}\left( {\sin \alpha + \mu \cos \alpha } \right)$$

D

$${\text{P}} = {\text{W}}\left( {\cos \alpha + \mu \sin \alpha } \right)$$

A body of weight W is required to move up the rough inclined plane whose angle of inclination with the horizontal is $$\alpha $$. The effort applied parallel to the plane is given by (where $$\mu $$ = $$\tan \varphi $$ = Coefficient of friction between the plane and the body)

A

$${\text{P}} = {\text{W}}\tan \alpha $$

B

$${\text{P}} = {\text{W}}\tan \left( {\alpha + \varphi } \right)$$

C

$${\text{P}} = {\text{W}}\left( {\sin \alpha + \mu \cos \alpha } \right)$$

D

$${\text{P}} = {\text{W}}\left( {\cos \alpha + \mu \sin \alpha } \right)$$

A body of weight ‘w’ placed on an inclined plane is acted upon by a force ‘P’ parallel to the plane which causes the body just to move up the plane. If the angle of inclination of the plane is ‘θ’ and angle of friction is ‘φ’, the minimum value of ‘P’, is

A

w sin (φ - θ)/cos φ

B

w sin (θ - φ)/cos φ

C

w cos (θ + φ)/cos φ

D

w sinθ cos(θ - φ)/sin φ

A body of weight w placed on an inclined plane is acted upon by a force P parallel to the plane which causes the body just to move up the plane. If the angle of inclination of the plane is $$\theta $$ and angle of friction is $$\varphi $$, the minimum value of P, is

A

$$\frac{{{\text{w}}\sin \left( {\varphi - \theta } \right)}}{{\cos \varphi }}$$

B

$$\frac{{{\text{w}}\sin \left( {\theta - \varphi } \right)}}{{\cos \varphi }}$$

C

$$\frac{{{\text{w}}\cos \left( {\theta + \varphi } \right)}}{{\cos \varphi }}$$

D

$$\frac{{{\text{w}}\sin \theta \cos\left( {\theta - \varphi } \right)}}{{\sin\varphi }}$$

From the given table, what is the percentage of students scoring 40 or more, but less than 70. Scores Less than 20 Less than 30 Less than 40 Less than 50 Less than 60 Less than 70 Less than 80 No. of Students 12 19 22 31 38 46 50

A

8%

B

56%

C

48%

D

96%

While discussing about friction, a teacher gave a number of examples to explain the concept. Some of the examples where friction is useful in our day-to-day life as quoted by the teacher are given below : A. We are able to write because of friction between the tip of the pen and the paper. B. We are able to walk because of friction between our feet and the ground. C. A ball thrown vertically upwards comes back to us due to friction. D. We are able to stop a moving vehicle by applying brakes because of friction. The correct examples were

A

A, B and C

B

B, C and D

C

C, D and A

D

D, A and B

Consider the following statements: 1. The kinetic friction is always less than the rolling friction. 2. The kinetic friction is always equal to the rolling friction. 3. The kinetic friction is always greater than the rolling friction. Which of the following statement is correct?

A

Both 1 and 2

B

Both 2 and 3

C

Only 3

D

All 1,2 and 3

If a body is lying on a plane whose inclination with the horizontal is less than the angle of friction, then i. a force is required to move the body upwards ii. a force is required to move the body downward iii. the body will not be in equilibrium The correct answer is

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