Please help me with this confusing physics question!!!?

Physics Guy · #1 (**permalink**) 04-26-2008, 09:52 PM

A 0.78 kg mass is moving horizontally with a speed of 8.0 m/s when it strikes a vertical wall. The mass rebounds with a speed of 4.2 m/s. What is the magnitude of the change in linear momentum of the mass? (kg*m/s)

LucaPacioli1492 · #2 (**permalink**) 04-26-2008, 10:04 PM

The initial momentum (toward the wall) = mv = (0.78kg)(8.0m/s) = 6.24 kg m/s
The momentum after collision with the wall = (0.78)(4.2m/s)
The change in momentum = 6.24 kg m/s + 3.28 kg m/s = 9.52kgm/s

Oliver T · #3 (**permalink**) 04-26-2008, 10:05 PM

Jeeze! I'd say a whole lot!!

billrussell42 · #4 (**permalink**) 04-26-2008, 10:06 PM

Change in speed is 8+4.2 = 12.2m/s
momentum is 12.2m/s x 0.78kg = 9.516 kgm/s

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