A block slides over a surface and it stops after covering a distance of P metres from the starting point. The same block is now slid over the same surface, but the surface is now lubricated and it stops at a distance of Q metres from the starting point.

Choose the correct option among the following.

P = Q as lubrication does not affect the friction between the surfaces.

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P < Q as lubrication reduces the friction between the surfaces.

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P > Q as lubrication reduces the friction between the surfaces.

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P < Q as lubrication increases the friction between the surfaces.

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Solution

The correct option is B
P < Q as lubrication reduces the friction between the surfaces.
Lubricants are the substances used to reduce the friction between two surfaces.

Hence due to less friction in the second case, the block will slide to a larger distance as compared to unlubricated surface i.e. P < Q.

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Similar questions

Q. A block slides over a surface and it stops after covering a distance of P metres from the starting point. The same block is now slid over the same surface, but the surface is now lubricated and it stops at a distance of Q metres from the starting point.

Choose the correct option among the following.

Q. A block of mass

2.0 kg

slides on a rough surface. At

t = 0

, its speed is

2.0 m/s

. It stops after covering a distance of

20 cm

because of the friction exerted by the surface on it. Find the work done by friction.

Q. A block of mass 2 kg slides on a rough surface at t=0, if speed is 2 m/s. It stops after covering a distance of 20 cm because of friction. Find work done by the friction.

Q. Assertion :A block of mass

m

starts moving on a rough horizontal surface with a velocity

v

. It stops due to friction between the block and the surface after moving through a certain distance. The surface is now tilted to an angle of

30^{0}

with the horizontal and the same block is made to go up on the surface with the same initial velocity

v

. The decrease in the mechanical energy in the second situation is smaller than that in the first situation. Reason: The coefficient of friction between the block and the surface decreases with the increase in the angle of inclination.

Statement I: A block of mass m starts moving on a rough horizontal surface with a velocity v. It stops due to friction between the block and the surface after moving a certain distance. The surface is now tilted to an angle of $30^{\circ}$ with the horizontal, and the same block is made to go up on the surface with the same initial velocity v. The decrease in the mechanical energy in the second situation is smaller than that in the first situation.
Statement II: The coefficient of friction between the block and the surface decreases with the increase in the angle of inclination.

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