signment Submission or this assignment, you submit answers by question parts. Th

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signment Submission or this assignment, you submit answers by question parts. The number of submissions remaining for each question part only changes if you submit or change the answer signment Scoring our best submission for each question part is used for your score. -17.69 points GloCP2 9.P039 My Notes O Ask Your Teacher A puck (mass mi 4.20 kg) slides on a frictionless table as shown in the figure below. The puck is tied to a string that runs through a hole in the table and is attached to a mass m2 = 12.6 kg. The mass m2 is initially at a height of h = 12.6 m above the floor with the puck traveling in a circle of radius r = 3.36 m with a speed of 12.6 m/s. The force of gravity then causes mass m2 to move downward a distance 1.26 m. (a) What is the new speed of the puck? m/s (b) What is the change in the kinetic energy of the puck? Submit Answer Save Progress es View Previous Question Question 13 of 13 Home My Assignments Extension Request

Explanation / Answer

a) First calculate the angular momentum of the puck:

L = r * m * v

r = 3.36

m = 4.20

v = 12.6

L = 188.81 Js

As there is no net torque working on the system, angular momentum is conserved, thus we can calculate the new velocity, with, again:

L = r * m * v

r = 3.36 - 1.26 = 2.1

m = 4.2

L = 188.81 Js (as calculated above)

Thus, v = L/mr = 188.81/(4.2*2.1)

=> v = 21.4 m/s

b) the energy before is:

E = 1/2 * m * v^2

m = 4.2

v = 12.6

E = 333.396 J

energy after:

m = 4.2

v = 21.4

E =961.716 J

Thus, the change in kinetic energy is:

961.716 – 333.396 = 628.32 J

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