It is easier to roll a barrel than pull it along the road. This statement is
A
False
B
True
C
Uncertain
D
Not possible
Easy
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B
True
b This phenomenon can be explained by the concept of friction. It is easier to roll a barrel than to pull it on the road because while pulling the barrel because rolling friction is less than sliding friction
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A uniform chain of length $L$ which hanges partially from a table, is kept in equilibrium by friction. The maximum length that can withstand without slipping is $l$ , then coefficient of friction between the table and the chain is
A block of mass $m$ is placed on a surface having vertical cross section given by $y=x^2 / 4$. If coefficient of friction is $0.5$ , the maximum height above the ground at which block can be placed without slipping is:
A rope of length $L$ and mass $M$ is being pulled on a rough horizontal floor by a constant horizontal force $F$ = $Mg$ . The force is acting at one end of the rope in the same direction as the length of the rope. The coefficient of kinetic friction between rope and floor is $1/2$ . Then, the tension at the midpoint of the rope is
A car of weight $W$ is on an inclined road that rises by $100\,m$ over a distance of $1\,Km$ and applies a constant frictional force $\frac {W}{20}$ on the car. While moving uphill on the road at a speed of $10\,ms^{-1},$ the car needs power $P.$ If it needs power $\frac {P}{2}$ while moving down hill at speed $v$ then value of $v$ is ........ $ms^{-1}$
A body of mass $'m'$ is launched up on a rough inclined plane making an angle of $30^{\circ}$ with the horizontal. The coeffcient of friction between the body and plane is $\frac{\sqrt{x}}{5}$ if the time of ascent is half of the time of descent. The value of $x$ is ..... .
The coefficient of static friction between two blocks is $0.5$ and the table is smooth. The maximum horizontal force that can be applied to move the blocks together is $\ldots \ldots . N$. (take $\left.g=10\, {ms}^{-2}\right)$
Two blocks $A$ and $B$ of masses $m_A = 1\,kg$ and $m_B = 3\,kg$ are kept on the table as shown in figure. The coefficient of friction between $A$ and $B$ is $0.2$ and between $B$ and the surface of the table is also $0.2.$ The maximum force $F$ that can be applied on $B$ horizontal, so that the block $A$ does not slide over the block $B$ is ........ $N$. [Take $g = 10\,m/s^2$ ]
$Assertion$ : On a rainy day it is difficult to drive a car or bus at high speed.
$Reason$ : The value of coefficient of friction is lowered due to wetting of the surface