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Physics
Friction
Given, 6 blocks of equal mass ‘m’ are placed in the arrangement as shown in the figure. The coefficient of friction between all the blocks are ‘u’ and the ground is smooth find the value of ‘F’ for which tension is >0 for string 2

Physics
Friction
Two blocks of masses ${M_1} = 4kg$ and ${M_2} = 6kg$ are connected by a string of negligible mass passing over a frictionless pulley as shown in the figure below. The coefficient of friction between the block ${M_1}$ and the horizontal surface is 0.4. When the system is released the masses ${M_1}$ and ${M_2}$ start accelerating. What additional mass $m$ should be placed over M so that the masses (${M_1}$ + $m$) slide with a uniform speed?

(A) 12kgs
(B) 11khs
(C) 10kgs
(D) 9kgs
Physics
Friction
A circular road of radius 1000 m has a banking angle $45^\circ$. If the coefficient of friction between tyre and road is 0.5, then the maximum safe speed of a car having mass 2000 kg will be
(A) 172 m/s
(B) 124 m/s
(C) 99 m/s
(D) 86 m/s
Physics
Friction
Determine the time in which the smaller block reaches the other end of the bigger block in the figure:

$(A)4{\text{ }}s$
$(B)8{\text{ }}s$
$(C)2.19{\text{ }}s$
$(D)13{\text{ }}s$
Physics
Friction
A body of mass $2kg$ is lying on a rough inclined plane of inclination ${30^ \circ }$ . Find the magnitude of the force parallel to the incline needed to make the block move
(a) up the incline
(b) down the incline.
Coefficient of friction $= 0.2$ .
Physics
Friction

Why is friction a necessary evil ?

Physics
Friction
A block of mass $m$ on a smooth horizontal surface is connected to a second mass $2m$ by a light cord over a light friction less pulley as shown. (Neglect the mass of the cord and the pulley). A force of magnitude ${F_0}$​ is applied to mass $m$ as shown. Neglect any friction. Find the value of force ​${F_0}$ for which the system will be in equilibrium

A.$mg$
B.$2mg$
C.$3mg$
D.$4mg$
Physics
Friction
Which of the following statements is correct about friction?
A) The coefficient of friction between a given pair of substances is largely independent of the area of contract between them
B) The friction force can never exceed the reaction force on the body from support of the surface.
C) Rolling friction is only slighting smaller than sliding friction
D) The main cause of friction is the irregularity of the surface in contact.
Physics
Friction
Block of mass $10kg$ is moving on an inclined plane with constant velocity $10m/s$. The coefficient of kinetic friction between the incline plane and block is:

A.$0.57$
B.$0.75$
C.$0.5$
D.None of these
Physics
Friction
A $40\,kg$ box rests on the horizontal floor of a truck which is initially at rest on a horizontal road. The coefficient of kinetic friction between the floor and the box is $0.2$. The truck at time $t = 0$ accelerates constantly at $5\,m{\text{ }}{s^{ - 2}}$ and the box is $6m$ away from the rear opening of the truck. Find the time $t$ when the box just falls off the floor of the truck.
Physics
Friction
Suppose you are driving a classic car, why should you avoid slamming on your brakes when you want to stop in the shortest possible distance? (Many modern cars have antilock brakes that avoid this problem).

Physics
Friction
Why is it easy to slip when there is water on the floor?
(A) The water is a lubricant and reduces the friction between your feet and the floor.
(B) The friction between your feet and the floor changes from kinetic to static friction.
(C) The water increases the friction between your feet and the floor.
(D) The friction between your feet and the floor changes from sliding kinetic friction to rolling kinetic friction.
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