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A 100 g particle moving with initial speed u strikes a second, identical 100 g particle that is initially at rest. If the total kinetic energy of the system after the collision is 0.2 J, what are the minimum and maximum possible values of u?

1. min = 2 m/s, max = 2*sqrt(2) m/s
2. min = 1 m/s, max = 2 m/s
3. min = 2*sqrt(2) m/s, max = 4 m/s
4. min = sqrt(2) m/s, max = 2 m/s

Correct answer: min = 2 m/s, max = 2*sqrt(2) m/s

Solution

For a fixed final KE of 0.2 J, the smallest u corresponds to no energy loss (elastic), and the largest u corresponds to maximum energy loss (perfectly inelastic).

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