A 1.2 kg mass is moving in a circle of radius 1.2 m on a flat frictionless table

Question

A1.2kg mass is moving in a circle of radius1.2m on a flat frictionless table at the end of a string. The speed of the mass is3.8m/s. The string routes through a hole in the center of the table and is held by you underneath the table.

A)What is the angular momentum of the mass?

B)What is the tension in the string?

C)If you pull on the string so that the radius of the circle decreases to one half its former value, what is the new tension in the string?

D)How much work did you do to reduce the radius by a factor of one-half?

Explanation / Answer

a)amgular momentum=mvr

=5.472

b)T=mv^2/r

=14.44 N

c)v1*r1=v2*r2

or v2=7.6 m/s

so T=mv^2/(0.5r)

=115.52 m/s

D)work done=0.5(mv^2-mv2^2)

=25.992 J

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