(1) A small block with a mass of 0.09 kg is attached on a cord passing through a hole in a frictionless, horizontal surf

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(1) A small block with a mass of 0.09 kg is attached on a cord
passing through a hole in a
frictionless, horizontal surface. The block is originally revolving
at a distance of 0.4 m from the
hole with a speed of 0.7 m/s. The cord is then pulled from below
gradually, shortening the radius
of the circle in which the block revolves to 0.1 m. At this new
distance, the speed of the block is
observed to be 2.8 m/s. (6 points)
(a)The tension in the cord in the final situation is given by
when the block
has speed » = 2.8m/s.
(b) The work done by the person who pulled on the cord is given
by