​Collisions and Motion

​It is your last chance to knock over the final bowling pin and win the game. You roll the heavy bowling ball toward the still pin, and it moves slowly down the lane. When the objects collide, the pin quickly shoots away from the collision. You win the game!

​Not all collisions result in the same changes in motion. The collision of the bowling ball and a bowling pin is different from the collision of two soccer balls. Even though the bowling ball hits the pin at a slower speed, the pin moves at a faster speed after the collision. Recall that the amount of energy a moving object has relates to its weight and speed. So, weight and speed also affect what happens when objects collide and transfer energy.

​A bowling ball has a greater weight than a bowling pin. So, when a slow bowling ball collides with pins, they will move at a faster speed. This is because weight and speed affect how energy transfers during a collision.

​Colliding with a Still Object of the Same Weight

​When a moving object collides with a still object of the same weight, the energy transfer causes the still object to move at the speed of the object that hit it. So, if a rolling soccer ball collides with a still soccer ball of the same weight, the still ball will gain the same energy of motion that the rolling ball lost. Since both balls are the same weight, the second ball will move at the same speed as the ball that collided with it.

​Colliding with a Still Object of a Different Weight

​When a moving object collides with a still object of a different weight, the energy transfer can affect the objects' speeds differently. A bowling ball is heavier than a bowling pin. When the ball collides with the pin, it transfers energy. The pin weighs less, so this energy makes it move faster than the ball.

​Colliding at the Same Speed

​When two objects moving at the same speed with the same weight collide head on, they each bounce back in the direction they came from at the same speed. Suppose you and a friend kick soccer balls toward each other at the same speed. After colliding, each ball will return toward its kicker at the same speed it was traveling.

​Colliding at Different Speeds

​When two objects of the same weight traveling at different speeds collide head on, they bounce backward. They each travel at the original speed of the other object. Think about kicking a soccer ball hard. Your friend kicks his ball gently. Your ball will move quicker and thus have more energy. After they collide, your ball will roll back to you with less energy and slower. Your friend's ball will roll back to him with more energy and quicker.

​These soccer balls have different speeds before they collide. After they collide, the ball that was faster now moves at the slower speed. The ball that was slower now moves at the faster speed.

​Answer Questions in TCI

Unit 2 Lesson 2 Section 2

​Make you you check out the interactive simulation at the end of the lesson before answering all questions.

You must use RACE Strategy when answering.

• Restate the question

• Answer the question in your OWN words.

• Cite Text to support your answer

• Explain (This is how I know....)