Assertion (A) Work done by friction on a body sliding down an inclined plane is positive.Reason (R) Work done is greater than zero it the angle between force and displacement is acute.

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

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

A smooth plane inclined at an angle θ with the horizontal as shown in the given figure. A body starts from rest and slides down on the inclined surface. The time taken by the body to reach the bottom is
Gravitational Force mcq question image

A

$$\frac{{\sqrt {2h} }}{g}$$

B

$$\sqrt {\frac{{2l}}{g}} $$

C

$$\frac{1}{{\sin \theta }}\sqrt {\frac{{2h}}{g}} $$

D

$$\sin \theta \frac{{\sqrt {2h} }}{g}$$

A body, resting on a rough horizontal plane required a pull of 181 N inclined at 30° to the plane just to move it. It was recorded that a push of 220 N inclined at 30°° to the plane just moved the body. Estimate the coefficient of friction.

A

0.17

B

0.2

C

0.5

D

0.75

If the angle of projection is double the angle of inclination ($$\alpha $$) of the plane on which particle is projected, the ratio of times of flight up the inclined plane and down the inclined plane, will be

A

$$\frac{1}{2}\,\cos \alpha $$

B

$$\frac{1}{2}\,\sin \alpha $$

C

$$\frac{1}{2}\,\tan \alpha $$

D

$$2\cos \alpha $$

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 $$\alpha $$. 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, resting on a rough horizontal plane required a pull of 181 N inclined at 30° to the plane just to move it. It was recorded that a push of 220 N inclined at 30° to the plane just moved the body. Estimate the weight of the body in N.

A

2000N

B

2500N

C

1000N

D

4000N

The elastic potential energy of a body is
1. Work done by the external force against the deforming force.
2. Work done against the external force by the deforming force.
3. The sum of work done by the external force and the deforming force.
Which one option is true?

A

Only 1

B

1 and 3

C

1, 2 and 3

D

None of these

A body will begin to move down an inclined plane, if the angle of inclination of the plane is ________ the angle of friction.

A

Equal to

B

Less than

C

Greater than

D

None of these

A body will begin to move down an inclined plane if the angle of inclination of the plane is _________ the angle of friction.

A

Equal to

B

Less than

C

Greater than

D

None of these

Assertion (A) Work done by friction on a body sliding down an inclined plane is positive.
Reason (R) Work done is greater than zero it the angle between force and displacement is acute.

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