Friction

Q. 25.A weight W rests on rough horizontal plane.if the angle of friction be theta, then calculate the least horizontal force that will move the body along the plane

Q. 54. A body of mass m is placed on a rough surface with coefficient of friction =mu inclined at theeta.If the mass is in limiting equilibrium then theeta =

Q. 128.A wedge with mass M rests on frictionless horizontal surface . A block with mass m is placed on the wedge . There is no friction between the block and wedge. A horizontal force F is applied to the wedge . What magnitude F must have if block is to remain at constant height above the table top ??

Q. A block of mass m is kept on a plank. Thecoefficient of friction between the plank and theblock is 1. The plank is slowly raised from one endso that it makes angle 0 with horizontal. The forceof friction acting on the plank when 0 30^° isFrAmy77777ban 30%Mg(1) J2Mg(2)23Mg(3)E2(4) Ma

Q. A block of weight 1 N rests on an inclined planeof inclination 0 with the horizontal. The coefficientof friction between the block and the inclined planeis u.The minimum force that has to be appliedparallel to the inclined plane to make the body justmove up the plane is

Q. 24.A wedge of mass M makes an angle theta with the horizontal .The wedge is placed on horizontal frictionless surface .A small block of mass M is placed on the inclined surface of wedge .What horizontal force F must be applied to the wedge so that force of friction between the block and wedge is zero

Q. Two bullets are fired simultaneously from the samelevel and in the horizontal direction over a lake.The speed of one bullet is 196 ms-1. Assume thatair friction is negligible and the lake is still. Thebullet which is faster will, compared to the slowerone, fall in the water

Q. nta uniform object ladder of length 3.5 m and weighing 250n is placed against a smoth vertical wall with its lower end 1.25 m from the wall . if coefficent of friction between the ladder and floror is 0.3 , then the frictional force acting on the ladder at that point of contact betweenh ladder and floorn ntn

Q. The velocity profile of a fluid over a flat plate is parabolic in nature. At a distance of $15\text{cm}$ from the plate, the velocity of fluid is maximum i.e $100\text{cm/s}$. Calculate the shear stress at a distance of $10\text{cm}$ from the plate if the viscosity of the fluid is $10\text{poise}$.

1. $4.53{\text{N/m}}^2$
2. $2.26{\text{N/m}}^2$
3. $2.35{\text{N/m}}^2$
4. None of these

Q. a rod is placed at an angle theta with the vertical. find the initial frictional force acting on it and the normal force ; provided no slippingtakes place.

Q. A solid disc and a ring, both of radius 10 cm are placed on a horizontal table simultaneously, with initial angular speed equal to 10 p rad s-1. Which of the two will start to roll earlier ? The co-efficient of kinetic friction is μ _k = 0.2.

Q. A cubical block of mass M and side a is placed on a rough horizontal plane . A force F is acting on the block at height 3a/4 from the bottom. The minimum value of coefficient of friction(μ) such that block topples without sliding will be-1) 2/3, 2)1/2, 3)3/4, 4)1/3

Q.

A man wants to move a iron box to the second floor using stairs. He tied a rope to the box and pulls it up a ramp placed over the stairs. The ramp is very smooth (no friction). What forces are acting on the box?

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Q. A block of mass $m$ is placed on a smooth inclined wedge ABC of inclination $\theta$ as shown in the figure. The wedge is given acceleration $a$ towards the right. The relation between $a$ and $\theta$ for the block to remain stationary on the wedge is

1. $a=\frac{g}{\cos ec\theta }$
2. $a=\frac{g}{\sin \theta }$
3. $a=g\cos \theta$
4. $a=g\tan \theta$

Q. By what factor will the flow rate of a viscous fluid through a pipe change, if the pipe radius is doubled, the fluid viscosity is doubled, the length is doubled and the pressure drop is reduced to a quarter of its previous value?

1. $4$
2. $16$
3. $\frac{1}{4}$
4. Doesn't change

Q.

Water flows steadily through a horizontal pipe of a variable cross-section. If the pressure of water is p at a point where the velocity of flow is $\upsilon$, what is the pressure at another point where the velocity of flow is $2\upsilon ;\rho$ being the density of water?

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Q. A block of weight W is pulled on a horizontal surface with a force making angle of theeta with the horizontal. If the angle of friction is alpha then the minimum force required to slide the block is

Q. What will be the total resistance offered to the flow of water by the system of pipe $1$, pipe $2$, pipe $3$ and pipe ignoring the joints? If all the pipes are of length $3\text{m}$ and radius $2\text{m}$ and '$\eta$' is viscosity of water. (Assume $\pi =3$)

1. $1.25\eta$
2. $3\eta$
3. $4.5\eta$
4. $9\eta$

Q. 46. Q. The upper half of an inclined plane of inclination Ө is perfectly smooth while lower half is rough. A block starting from rest at the top of the plane will again come to rest at the bottom, if the coefficient of friction between the block and lower half of the plane is given by 1) 2/ tan Ө 3) 2tan Ө 4) tan Ө 5) 1/ tan Ө

Q. A solid cylinder of mass $m$ and radius $r$ starts rolling down an inclined plane of inclination $\theta$. Friction is sufficient to prevent slipping. Find the speed of its centre of mass when its centre of mass has fallen a height $h$.

Q. What is the average friction force when a person has a usual 1 km walk?

Q. A block of mass 2 kg rest on a horizontal surface .if a horizontal force of 5N is applied on a block the frictional force on it is (muK =0.4 , muS=0.5)
A) zero
B) 8N
C) 10N
D) 5N

Q. Four identical rods of mass $M=6\text{kg}$ each are welded at their ends to form a square and then welded to a massive ring having mass $M=4\text{kg}$ and radius $R=1\text{m}$. If the system is allowed to roll down the incline of inclination $\theta ={30}^{\circ }$.


The minimum value of friction coefficient to prevent slipping is

1. $\frac{5}{7}$
2. $\frac{5}{12\sqrt{3}}$
3. $\frac{5\sqrt{3}}{7}$
4. $\frac{7}{5\sqrt{3}}$

Q. Why for rolling f≤μ R and for sliding f≥μ R . Here f represents frictional force and bodies are on inclined plane making an angle θ with the ground

Q. A block of mass $m$ is placed on a smooth inclined wedge ABC of inclination $\theta$ as shown in the figure. The wedge is given acceleration $a$ towards the right. The relation between $a$ and $\theta$ for the block to remain stationary on the wedge is

1. $a=\frac{g}{\cos ec\theta }$
2. $a=\frac{g}{\sin \theta }$
3. $a=g\cos \theta$
4. $a=g\tan \theta$

Q. A hollow sphere is projected horizontally along a rough surface with speed $v$ and angular velocity ${\omega }_0$, find out the ratio $\left(\frac{v}{{\omega }_0}\right)$, so that the sphere stops moving after some time.

1. $\frac{2R}{3}$
2. $\frac{4R}{3}$
3. $\frac{7R}{3}$
4. $R$