From the examples below choose only two and indicate the type of collision each represents. Justify each choice using concepts from this unit.

1. Two billiard balls are moving toward each other along an essentially frictionless surface and collide head-on.
2. While distracted by the sun, a driver heading eastbound doesn't see a stop sign and proceeds to drive through an intersection. Meanwhile, another car travelling southbound enters the intersection and collides with the eastbound vehicle. Both cars remain together after the initial contact occurs.
3. Standing at the baseline of a tennis court, a tennis player tosses a tennis ball over her head swings at the ball. The racquet hits the tossed ball and travels to the other side of the tennis court.
4. A rubber ball is thrown at an aluminum can. Hitting the can, the ball causes a dent in the can.

3. From the examples below choose only two and indicate the type of collision each represents. Justify each choice using concepts from this unit. i. Two billiard balls are moving toward each other along an essentially frictionless surface and collide head-on. ii. While distracted by the sun, a driver heading eastbound doesn't see a stop sign and proceeds to drive through an intersection. Meanwhile, another car travelling southbound enters the intersection and collides with the eastbound vehicle. Both cars remain together after the initial contact occurs. iii. Standing at the baseline of a tennis court, a tennis player tosses a tennis ball over her head swings at the ball. The racquet hits the tossed ball and travels to the other side of the tennis court. iv. A rubber ball is thrown at an aluminum can. Hitting the can, the ball causes a dent in the can