Which of these systems is NOT an “isolated system” to which conservation of momentum can be applied? 1. A billiard ball collides with another billiard ball on a level pool table. (Ignore friction with the table during the instant of the collision.) System: the two balls
2. A ball falls freely toward the ground. (Ignore air friction.) System: the ball and the earth
3. All of these in fact are isolated systems.
4. A single car slips on an icy road. (Friction with the ice is negligible.) System: the car
5. Two cars slipping on an icy road collide with one another. (Friction with the ice is negligible.) System: the two cars
6. A ball falls freely toward the floor. (Ignore air friction.) System: the ball
7. Two masses connected by a spring oscillate on a frictionless tabletop. System: the two masses and the spring