A horizontal force of $4\,N$ is needed to keep a block of mass $0.5\, kg$ sliding on a horizontal surface with a constant speed. The coefficient of sliding friction must be :- $[g = 10\, m/s^2]$
$\Rightarrow \mu=\frac{F_{e x t}}{m g}=\frac{4}{0.5 \times 10}$
$\Rightarrow \mu=0.8$
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A car having a mass of $1000\, kg$ is moving at a speed of $30\, metres/sec$. Brakes are applied to bring the car to rest. If the frictional force between the tyres and the road surface is $5000$ newtons, the car will come to rest in ........ $\sec$
$Assertion$ : There is a stage when frictional force is not needed at all to provide the necessary centripetal force on a banked road.
$Reason$ : On a banked road, due to its inclination the vehicle tends to remain inwards without any chances of skidding.
A lift is moving downwards with an acceleration equal to acceleration due to gravity. $A$ body of mass $M$ kept on the floor of the lift is pulled horizontally. If the coefficient of friction is $\mu $, if the lift is moving upwards with a uniform velocity, then the frictional resistance offered by the body is
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Assuming the coefficient of friction between the road and tyres of a car to be $0.5$, the maximum speed with which the car can move round a curve of $40.0\, m$ radius without slipping, if the road is unbanked, should be ......... $m/s$
A block of mass $m$ is pressed against a vertical surface by a spring of unstretched length $l$ . If the coefficient of friction between the block and the surface is $\mu $. Choose the correct statement.
In figure, two blocks $M$ and $m$ are tied together with an inextensible and light string. The mass $M$ is placed on a rough horizontal surface with coefficient of friction $\mu$ and the mass $m$ is hanging vertically against a smooth vertical wall. The pulley is frictionless. When the downward acceleration of the elevator becomes equal to $g$, then