The problem is very unclear. The way I understand it is like this:
The yarn is rolling toward the cat, and from the instant the cat first touches
the yarn, it moves 17.5 cm 2 sec, in the direction opposite to the way it was
rolling.
Average speed during the 2 seconds after the bump = 17.5 / 2 = 8.75 cm/s .
Average speed = (1/2) (final speed away from the cat - 1 cm/sec towards the cat)
8.75 cm/s = (1/2) (final speed + 1)
Multiply each side by 2 :
17.5 = final speed + 1
Final speed = 16.5 cm/s
Acceleration = (change in speed) / (time for the change)
Acceleration = (16.5 + 1) / (20) = 0.875 cm/s² .
My confidence level in this one is not excessive, but I'll submit it anyway,
and somebody else can explain to me where I went wrong.
