Purpose
This interactive uses a virtual pool table to explore conservation of linear momentum and collisions.

Using the Interactive
Configure the interactive using the CONTROLS and BEFORE/AFTER DISPLAY templates on the right-hand side.

• Next Mass: This slider sets the mass of the next ball placed on the table.
• Play/Pause, Reset, Step: These buttons control the animation.
• Show Velocity Vectors: If checked, the interactive displays the velocity vectors of the balls on the table as they move.
• Allow Pockets: If checked, the table will have pockets into which the balls may fall.
• Enable Friction: If checked, the balls will slow down as they move across the table.
• Restrict to 1 Dimension: Controls whether the collisions are one or two-dimensional.
• Show Grid: If checked, displays a coordinate grid on the pool table.
• Presets: Select among two preset animations to play.
• Freeze for Collisions: If checked, the animation freezes every time a collision between two balls occurs.
• Velocity, Comb, Vel., Momentum, or Comb. Mtm.: If checked, these vectors display in the before and after windows. Velocity and Momentum displays the vectors for each ball in the collision; Combo. Vel and Combo. Mtm displays the sum of the velocities and momentums of the two balls.

1			Select Restrict to 1 Dimension. Deselect COMB. MTM under BEFORE/AFTER DISPLAY at the bottom right. To place a ball on the table: Put the cursor over the table (a ghost ball appears) → click to set the ball in position → move the mouse to set the initial velocity of the ball → click to set the ball in motion. Set MASS to 10.0 and follow the above procedure to place a second ball on the table. After they collide, the motion will freeze. Beneath the pool table the before and after pictures will show the momentum vectors of each ball. Note the before and after windows; will the total momentum before and after the collision be the same?
			A)	yes
			B)	no
2			Note the before and after windows; will the momentum of each individual ball before and after the collision be the same?
			A)	yes
			B)	no
3			Do the total momentums before and after appear to have the same magnitude?
			A)	yes
			B)	no
4			Click somewhere over the pool table to continue the motion. Deselect the MOMENTUM checkboxes and select the COMB. VEL. checkbox. How do the total velocities before and after the collision compare?
			A)	They are the same.
			B)	They are different.