Equipment Marbles Stopwatch Block

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1 Name 5 March 2018 Ms. Kelly Physics Marble ous Momentum Lab Introduction Existing theory asserts that momentum is conserved. In the first part of this two-part laboratory you will explore qualitatively the conservation of momentum. In the second part you will calculate the momentum before a collision and the momentum after a collision between two small marbles. Momentum is the mass (grams) multiplied by the velocity (cm/s). (P = m v ) Conservation means "stays the same." Usually this means, "the momentum after a collision is the same as the momentum before the collision." Equipment Marbles Stopwatch Block Rulers Tape Part One: Conservation of Momentum: Rolling Marbles In part one we explore a simple system. Five marbles sit touching each other on the flat portion of a marble track. The marble track is made of two plastic rulers with grooves to guide the marbles. One or more marbles are released from an elevated end of the track. Procedure for Part One & Questions 1. Release one marble. How many marbles are ejected from the group? 2. Release two marbles. How many marbles are ejected from the group? 3. Repeat for three, four,... marbles. 4. How is the number in related to the number out? 5. Release one marble from half-way up the ramp. Is the inbound marble fast or slow? Is the ejected marble fast or slow? INBOUND EJECTED 6. Send a marble in at high speed. Is the ejected marble fast or slow? 7. How is the speed (velocity) in related to the speed (velocity) out? Part Two Introduction In part two the event is a collision between two marbles. One marble at rest is hit by another marble rolling down the ramp. The momentum of the one marble rolling down the ramp before the collision should be equal to the sum of the momenta of the marbles after the collision.

2 The marble coming into the collision is called the "inbound" marble in this laboratory. To keep the marbles straight, this lab will refer to the inbound marble as the blue marble and the marble that is sitting still on the track at the start as the white marble. Your marbles may be different in color! Equations for Part 2: 1) p before = p after 2) m 1 v 1 + m 2 v 2 = m 1 v 1 + m 2 v 2 In part two you will measure all of the variables above and then plug the values into equation # 2 above. If the left side is equal to the right side, your results show that momentum is conserved. If the left and right side are within 10% of each other, your results will also be accepted. Procedure for Part Two ** Measure mass of two marbles on electric scale. Record Note ** To measure the speed accurately, you will first roll the blue marble five times measuring the length of time for the marble to roll across the 30 cm flat section of track on the "second" ruler. This means measuring five time durations before the collision, and ten measurements for the durations after the collision. Before : Inbound marble speed measurement procedure 1. Roll the inbound blue marble down the track by itself, releasing it from 0.0 cm at the top of the ramp track. 2. Measure the time for the blue marble to cover the 30.0 cm along the flat ruler. The two marbles below show the distance over which to measure the time for the blue marble. 3. Repeat this five times to get the average time for the blue marble prior to being involved in the collision. Record

3 You will measure the speed on the flat section ONLY, since the marble is accelerating on the slope. You only want to know the speed of the marble at the bottom of the slope, because that is the speed at which the blue marble will collide with the white marble. Mean time (t 1 ) from table above: s 4. Calculate the momentum of the inbound blue marble below. After : Outbound marble speeds measurement procedure Set up the marbles to collide, as shown below. 1. Place the blue (m1) at 0.0 cm on the ramp track. 2. Place the white (m2) on the flat track at 0.0 cm. 3. In the image above m1 is on the right, m2 is on the left. 4. Do a practice run of the collision. Both marbles will roll off the track. 5. Speed of the white m2 marble after collision: Rerun the collision, timing the duration (time) for the white marble to travel 30 cm. Repeat the collision four more times, measuring the duration for the white marble to travel 30 cm to the end of the track. 6. Speed of the blue m1 marble after collision: Rerun the collision, timing the duration (time) for the BLUE marble to travel 30 cm. Repeat the collision four more times, measuring the duration for the blue marble to travel 30 cm to the end of the track. The above will require making five time measurements of the blue marble and five of the white marble. Use these measurements to determine the mean time for each. The next two tables provide a place to record data.

4 Is the momentum of the inbound blue marble equal to the sum of the momenta of the blue and white marbles after the collision? How close are the results? Use the percentage change formula to determine the change in momentum Calculating Percent Error Formula Work Answer Percentage error Δ% = ( sum of momenta after momentum before ) / momentum before %

5 Analysis & Discussion (Respond in complete sentences) What did you find was momentum conserved? What is the percentage gain or loss in momentum? Where is the momentum coming from or going to if anywhere? Is your result within 10% uncertainty? What are some sources of error that may have affected your results? Discuss what the conservation of momentum and energy means for you in light of the laboratory that you performed today. Be comprehensive in your response.