arthham

JEE Advanced 2011 · Work, Energy and Power

A block of mass 0.18 kg is attached to a spring of force-constant 2N/m.2 N/m. The coefficient of friction between the block and the floor is 0.1. Initially the block is at rest and the spring is unstretched. An impulse is given to the block as shown in the figure. The block slides a distance of 0.06 m and comes to rest for the first time. The initial velocity of the block in m/sm/s is V=N/10.V = N/10. Then N is

Answer: 44

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Written solution

Step 1: Identify the given parameters.

The physical constants and initial conditions of the system are given.

m=0.18 kgm = 0.18 \text{ kg} k=2 N/mk = 2 \text{ N/m} μ=0.1\mu = 0.1 d=0.06 md = 0.06 \text{ m} g=10 m/s2g = 10 \text{ m/s}^{2}

Step 2: Apply the work-energy theorem.

The initial kinetic energy of the block is converted into the potential energy stored in the spring and the work done against friction.

12mV2=12kd2+μmgd\frac{1}{2}mV^{2} = \frac{1}{2}kd^{2} + \mu mgd

Step 3: Solve for the initial velocity VV.

Rearrange the equation to express V2V^{2} in terms of the known variables.

V2=kmd2+2μgdV^{2} = \frac{k}{m}d^{2} + 2\mu gd

Substitute the given values into the equation.

V2=20.18(0.06)2+2(0.1)(10)(0.06)V^{2} = \frac{2}{0.18}(0.06)^{2} + 2(0.1)(10)(0.06) V2=0.04+0.12V^{2} = 0.04 + 0.12 V2=0.16V^{2} = 0.16 V=0.4 m/sV = 0.4 \text{ m/s}

Step 4: Find the value of NN.

Equate the calculated velocity to the given expression V=N10V = \frac{N}{10}.

N10=0.4\frac{N}{10} = 0.4 N=4N = 4

Answer: N=4N = 4

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