Lab conservation of momentum answers

1. Part I: Measure the Carts o  To find the length of the purple cart, use your mouse to drag the cart over the caliper in the upper left corner of the lab. Convert the length to the SI unit of meters, then record your result in the table below. Repeat the procedure for the green cart. o  These measurements will stay the same as long as you don’t refresh the screen or click the button to start a new experiment. If you don’t complete the lab if one sitting and have to load the lab page again, the lengths will change. If this happens, you will need to measure them again and use the new values for the remainder of the lab. o o o o • Length of purple car: Mass of purple car: Length of green car: Mass of green car:  These measurements will stay the same as long as you don’t refresh the screen or click the button to start a new experiment. If you don’t complete the lab if one sitting and have to load the lab page again, the lengths and masses will change. If this happens, you will need to measure them again and use the new values for the remainder of the lab. Part II: Determine the Carts’ Velocities • •  Select “same direction” from the Carts’ Direction menu and “inelastic” from the Collision Behavior menu.  Click Start Carts to put the carts in motion. The red numbers you will soon see tell you how many seconds it took each cart to pass through that photogate. If you lose track of which photogate is measuring which cart, notice the purple and green arrows labelling each; a half purple/half green arrow is used when both carts were stuck together as they passed through. You can also click Start Carts if you want to watch the collision again. • •  Record your times in the data table at the top of the next page. Also copy the lengths from part I. Be sure to add the lengths of the two carts when the carts are stuck together.  Calculate each cart’s velocity and enter it in the table as well. Elapsed time Length Velocity Purple cart before collision Green cart before collision Carts stuck together after collision Part III: Calculating Momentum  Use the fact that momentum equals mass times velocity to calculate the momentum of each cart. Remember to add the masses when the carts are stuck together. Mass Velocity (from part II) Momentum Purple cart before collision Green cart before collision Carts stuck together after collision • •  Calculate the total momentum of the two carts before and after the collision.  You should find that the total momentum before and after the collision is identical (at least to within rounding errors.) If you don’t, you should find out what went wrong and correct it before you complete the next part. Part IV: The Elastic Collision • •  This time, set the Carts’ Direction to opposite and the Collision Behavior to elastic. Repeat the same steps as in part II and III. (The data table is at the top of the next page.)  When you calculate the velocities and momenta, signs matter. Make sure that carts that are moving to the left have negative velocities. If you lose track of which direction the carts were going for each photogate, you have the arrows to help you, and you can click Start Carts to watch the collision again. Purple cart’s momentum Green cart’s momentum -------------------- ---------------------- Before collision After collision Total momentum Elapsed time Length Velocity (with sign!) Purple cart before collision Green cart before collision Purple cart after collision Purple cart before collision Mass Velocity Momentum Purple cart before collision Green cart before collision Purple cart after collision Purple cart before collision Purple cart’s momentum Before collision After collision Part V: One More Case Green cart’s momentum Total momentum Repeat the experiment once more, this time with any combination of Carts’ Direction and Collision Behavior you have not used already. Record which settings you use, then complete the calculations as before. Carts’ Direction ___________________________ Collision Behavior