MEDIUM
JEE Main
IMPORTANT
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In the figure shown below, a lead brick rests horizontally on cylinders A and B. The areas of the top faces of the cylinders are related by AA=2.2AB, the Young's moduli of the cylinders are related by EA=2.2EB. The cylinders had identical lengths before the brick was placed on them. What fraction of the brick's mass is supported a by cylinder A and b by cylinder B? The horizontal distances between the center of mass of the brick and the centerlines of the cylinders are dA for cylinder A and dB for cylinder B. c What is the ratio dA/dB?

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Important Questions on Equilibrium and Elasticity

EASY
JEE Main
IMPORTANT

In the figure shown below, one end of a uniform beam of mass 40.0 kg is hinged to a wall, the other end is supported by a wire that makes angles θ=30.0° with both wall and beam. Find a the tension in the wire and the b magnitude and c angle from the horizontal of the force of the hinge on the beam.

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EASY
JEE Main
IMPORTANT
1500 kg load is hung from the free end of a horizontal aluminum rod of length 7.0 cm, diameter 9.6 cm and negligible mass. The other end of the rod is fixed in place. The shear modulus of aluminum is 3.0×1010 N m-2. Find a the shear stress on the rod and b the vertical deflection of the rod's free end.
EASY
JEE Main
IMPORTANT

In the figure shown below, a cord with negligible mass suspends a uniform ball against a frictionless vertical wall. The ball's mass is 0.250 kg, its radius is 4.20 cm and the vertical distance L between the ball's center and the cord attachment on the wall is 8.00 cm the cord's tension and (b) the magnitude of the normal force on the wall from the ball? (Take 9=9.8 m s-2)

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MEDIUM
JEE Main
IMPORTANT
A cubical box is filled with sand and weighs 520 N. We wish to "roll" the box by pushing horizontally on one of the upper edges. a What minimum force is required? b What minimum coefficient of static friction between box and floor is required? c If there is a more efficient way to roll the box, find the smallest possible force that would have to be applied directly to the box to roll it. (Hint: At the onset of tipping, where is the normal force located?)
EASY
JEE Main
IMPORTANT

Forces F1, F2 and F3 act on the structure, as shown in the figure in an overhead view. We wish to put the structure in equilibrium by applying a fourth force, at a point such as P. The fourth force has vector components Fn and Fv. We are given that, a=2.0 m, b=3.0 m c=1.0 m, F1=30 N, F2=10 N and F3=5.0 N. Find a Fhb Fv and c d.

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EASY
JEE Main
IMPORTANT
An automobile with a mass of 1360 kg has 3.35 m between the front and rear axles. Its center of gravity is located 1.85 m behind the front axle. With the automobile on level ground, determine the magnitude of the force from the ground on a each front wheel (assuming equal forces on the front wheels) and b each rear wheel (assuming equal forces on the rear wheels).
HARD
JEE Main
IMPORTANT

In the figure shown below, a 55 kg climber is in a lie-back climb along a fissure, with hands pulling on one side of the fissure and feet pressed against the opposite side. The fissure has width w=0.20 m and the center of mass of the climber is a horizontal distance d=0.40 m from the fissure. The coefficient of static friction between the hands and the rock is μ1=0.45 and between the boots and the rock is μ2=1.2. (a) What is the least horizontal pull by the hands and push by the feet that will keep the climber stable? (b) For the horizontal pull of (a), what must be the vertical distance h between the hands and the feet? If the climber encounters a wet rock, so that μ1 and  μ2 are reduced, what happens to (c) the answer to (a) and (d) the answer to (b)?

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MEDIUM
JEE Main
IMPORTANT

The figure below shows an approximate plot of stress versus strain for a spider-web thread, out to the point of breaking at a strain of 2.00. The vertical axis scale is set by values a=0.10 GN m-2, b=0.30 GN m-2. Assume that the thread has an initial length of 0.80 cm, an initial cross-sectional area of  8.0×10-12 m2, and (during stretching) a constant volume. The strain on the thread is the ratio of the change in the thread's length to that of the initial length, and the stress on the thread is the ratio of the collision force to that of the initial cross-sectional area. Assume that the work done on the thread by the collision force is given by the area under the curve on the graph. Assume also that when the single thread snares a flying insect, the insect's kinetic energy is transferred to the stretching of the thread. (a) How much kinetic energy would put the thread on the verge of breaking? What is the kinetic energy of (b) a fruit fly of mass 6.00 mg and speed 1.70 m s-1 and (c) a bumble bee of mass 0.388 g and speed 0.420 m s-1? Would (d) the fruit fly and (e) the bumble bee break the thread?

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