Which of the following describes the treatment in an investigation?
1. a controlled test designed to answer a question or solve a problem
2. the factor that responds to change
3.the factor that is kept constant
4. the factor that is changed in order to observe a response

On a frictionless air track, a blue glider with mass 0.200 kg is moving to the right with a speed of 8.00 m/s. it strikes a red glider that has mass 0.600 kg and that is initially at rest. after the collision, the blue glider is moving to the left with a speed of 3.00 m/s.(a) what are the magnitude and direction of the velocity of the red glider after the collision? (b) is this collision elastic?