A block of dry ice is attached to a brink by a massless string. The system is pu

Question

A block of dry ice is attached to a brink by a massless string. The system is pushed across a slate tabletop with a horizontal force, so that the system has a constant speed of 10 m/s. The dry ice floats on a cushion of gas so that friction between the ice and the table is negligible. The coeffecient of kinetic friction between the brink and the table is muK = 0.75.

a. Find the power that must be supplied by the hand to keep the system moving at v = 10 m/s.

b. The hand suddenly stops pushing on the system. The ice and brink system gradullay slow and them come to a complete stop. How far does the system slide after the hand stops pushing?

Explanation / Answer

a) Force that must be applied to mantain constant speed, F = mue_k*N

= 0.75*20*9.8

= 147 N

so, Power supplied = F*v

= 147*10

= 1470 Watts <<<<<---------ANswer

b) Frictional force acting on the system = 147 N

Now Apply , Workdone by friction = change in kinetic energy of the system

F*d*cos(180) = 0.5*(m1+m2)**(vf^2 - vi^2)

-F*d = -0.5*(m1+m2)*vi^2

d = 0.5*(m1+m2)*vi^2/F

= 0.5*(20+10)*10^2/147

= 10.2 m <<<<<<<---------ANswer

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