Momentum bar chart

NAME_________________ Collisions in 1D Elastic, Conservation of Momentum and Momentum Bar Charts. Instructions on editing and saving PDFs: 1. This lab is in pdf format. Use Acrobat Reader to open it. You can then type your answers in the answer blanks. 2. Predict the bars in each bar chart. A toolbar lies along the right side of the Acrobat Reader window. Click the ‘Comment’ tool ( ). A ‘Comment’ toolbar should appear along the top of the window. Click the ‘Drawing Tools’ button ( ), then select ‘Rectangle’ to draw the bars of the bar chart. 2. Draw the blocks or Freebody diagrams. Click the ‘Drawing Tools’ button ( ), then select ‘Arrow’ to draw the forces. To label the forces, either click the ‘Use Drawing Tool’ tool ( ), or if you prefer, use the ‘Text Box’ tool ( ). Don’t worry about making the force subscripts look like subscripts. 3. Draw the correct bar chart using the ‘Use Drawing Tool’ tool ( ) 4. If the correct bar chart doesn’t match your prediction, reflect on what made you predict incorrectly. 5. When you are done with the lab, save it (i.e., save your comments) and submit it via Canvas. Introduction Momentum is defined as: p = mv For a constant force, impulse is defined as: J = F Δt Both momentum and impulse are vector quantities. Notice that momentum is defined as the product of a scalar (the mass) and a vector (the velocity). Since the mass is always positive, the momentum always has the same direction as the velocity. Similarly, for a constant force, the direction of the impulse on an object is always the same as the direction of the force acting on that object since the time interval (t) is always positive. The relationship between momentum and impulse (called the impulse-momentum theorem) is: Jnet = pf – pi → pi + Jnet = pf The impulse momentum theorem is applied to a system (i.e., a collection of interacting objects). In words, the impulse-momentum theorem states that any net impulse delivered to a system goes directly into changing the linear momentum of that system. The total momentum of a system is determined by adding the momenta of each of the objects in the system (vector addition!). The net impulse is determined by inserting the net force acting on the system into the definition of impulse. The net force on a system is the sum of all external forces (i.e., the force exerted by objects outside of the system) since internal forces (i.e., forces exerted by objects inside of the system due to interactions between objects) come in equal and opposite action-reaction pairs and hence cancel. Collision problems are often shown as prior and post collisions. Momentum is conserved, meaning that p = pf – pi = 0, this is related to total initial moment pi (before to the collision), and final momentum pf (after to the collision). 1 Experiment 1 (Elastic Collison) A red puck (0.5kg) is initially sliding to the right at 1m/s on a frictionless surface and green puck (1.5kg) is at rest. After the collision, the green puck is moving to the right at 0.5m/s. The system consists of both pucks. Predict the momentum and velocity of the red puck after the collision. The questions below are intended to help you correctly predict your first impulse momentum bar chart. Ask yourself similar questions in all subsequent experiments. Remember that since p = mv, the direction of the momentum is always the same as the direction of the velocity. 1. Initially the red puck is moving to the right. What is the direction of red puck’s initial momentum vector? ____________ (left, right, or zero momentum). • This momentum is____________. (positive, negative, or zero). 2. Initially the green puck is not moving. What is the direction of green puck’s initial momentum vector? ____________ (left, right, or zero momentum). • This momentum is____________. (positive, negative, or zero). 3. After the collision, the green puck is moving to the right. What is the direction of green puck’s final momentum vector? ____________ (left, right, or zero momentum). • This momentum is____________. (positive, negative, or zero). Draw a Freebody Diagram of the two pucks at the instant when the red puck is impacting the right side of the green puck. Red Puck Green Puck to test your 4. The total net force in the horizontal direction during the impact is____________.