# Conservation of linear momentum and angular momentum.

1. The 20-lb cart B is supported on rollers of negligible size. If a 10-lb suitcase A is thrown horizontally on it at 10 ft/s, determine the time t and the distance B moves before A stops relative to B. The coefficient of kinetic friction between A and B is μk =0.4.

2. Determine the magnitude of the angular momentum of the 2.5-kg particle about point O.

a. 104 (kg m2)/s

b. 182 (kg m2)/s

c. 262 (kg m2)/s

See attached file for full problem description.

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#### Solution Preview

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1. The 20-lb cart B is supported on rollers of negligible size. If a 10-lb suitcase A is thrown horizontally on it at 10 ft/s, determine the time t and the distance B moves before A stops relative to B. The coefficient of kinetic friction between A and B is μk =0.4.

The friction force is the tangential reaction between the two surfaces in contact which will try to stop the relative motion between the surfaces. Hence the friction will act backward on the suitcase and an equal and opposite (forward) friction force will act on the cart. The force on the suitcase will ...

#### Solution Summary

First problem is based on conservation of linear momentum, work and energy.

Second one is a good problem to determine angular momentum of an object in three dimensional space.