A block of mass 0.18 kg is attached to a spring of force-constant 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 un-stretched. 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/s is V=N/10. Then N is
Answer: 4
Solution
By work-energy theorem: −21kx2−μmgx=−21mV2. Substituting values: −21(2)(0.06)2−0.1(0.18)(10)(0.06)=−21(0.18)V2. Solving: 0.0036+0.0108=0.09V2⇒V2=0.16⇒V=0.4 m/s =104 m/s. Therefore N = 4.