Question

# A small block on a frictionless, horizontal surface has a mass of 2.50×10−2 kg . It...

A small block on a frictionless, horizontal surface has a mass of 2.50×10−2 kg . It is attached to a massless cord passing through a hole in the surface (Figure 1) .The block is originally revolving at a distance of 0.300 mfrom the hole with an angular speed of 2.99 rad/s . The cord is then pulled from below, shortening the radius of the circle in which the block revolves to 0.150 m. Model the block as a particle.

-Find the change in the Kinetic Energy of the block

given

mass of 2.50 X 10−2 kg

distance of 0.300 m

radius of the circle in which the block revolves to 0.150 m

the kinetic energy

K1 = 0.5 I 12

= 0.5 X m X r12 X 12

= 0.5 X 0.025 X 0.32 X 2.992

K1 = 0.010057 J

2 = ( 0.3 / 0.15 ) X 2.99

K2 = 0.5 I 22

= 0.5 X m X r22 X 22

= 0.5 X 0.025 X 0.152 X 5.982

K2 = 0.010057 J

the change in the Kinetic Energy of the block is = 0.010057 - 0.010057

the change in the Kinetic Energy of the block is zero

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