Two disks are initially at rest, each of mass M = 2 kg, connected by a string be

Question

Two disks are initially at rest, each of mass M = 2 kg, connected by a string between their centers, as shown in the figure. The disks slide on low-friction ice as the center of the string is pulled by a string with a constant force F = 13 N through a distance d = 2.8 m. The disks collide and stick together, having moved a distance b = 1.6 m horizontally.

(a) What is the final speed of the stuck-together disks?
vf = ???? m/s

(b) When the disks collide and stick together, their temperature rises. Calculate the increase in internal energy of the disks, assuming that the process is so fast that there is insufficient time for there to be much transfer of energy to the ice due to a temperature difference. (Also ignore the small amount of energy radiated away as sound produced in the collisions between the disks.)
Einternal = ???? J

Explanation / Answer

Energy principle to the point mass system

1/2 ( 2M) V^2 = Fb ( where V is teh velocity of center of mas after the disks stuck)

v^2 = Fb/M

v = sqroot ( Fb/M) = sqroot ( 13 x 1.6/ 2) = 3.225 m/s apprx

b) Einternal = 13 ( 2,8 - 1.6) = 15.6 J

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