Lab Assignment 6: Momentum
Collisions and momentum are something we experience everyday. Most of the collisions in our life are benign – bumping into a colleague in the hall, enjoying an evening of bowling, or competing in a billiards tournament. Some collisions, such as automobile accidents, are more serious. In these cases, advances in safety technology that leverage understanding of impulses and momentum have dramatically reduced fatalities. In this lab we will explore the concepts of impulse and momentum.
This activity is based on Lab 12 of the eScience Lab kit.
Our lab consists of two main components. These components are described in detail in the eScience manual. Here is a quick overview:
- In the first part of the lab, you will experiment with nearly elastic collisions using marbles.
- In the second part of the lab, you will put on your safety engineer’s hat and design a safe landing zone for an egg.
Take detailed notes as you perform the experiment and fill out the sections below. This document serves as your lab report. Please include detailed descriptions of your experimental methods and observations.
· Instead of using a paper chute in the marble experiment, you can “flick” the marble(s) down the ruler groove to the stationary line of marbles as in this image:
[img width=”180″ height=”251″ src=”file:///C:/Users/srarin/AppData/Local/Temp/msohtmlclip1/01/clip_image002.jpg” alt=”Description: Physics Lab 6 002″ v_shapes=”Picture 1″>
· I recommend using hard-boiled eggs in the second component of the lab activity. They are less messy and serve as a handy snack after you complete the lab.
Material and Methods
Based on your results from the marble experiment, please answer the following questions:
1. What kind of collision is exhibited by the marbles in this experiment, and why?
2. When one marble hit the end of the line of marbles, how many shot off the other end? Describe the momentum of the set of marbles before and after the collision (assume elastic collisions).
3. How did the speed of the marble that comes off the end of the line change as you increased the speed of the marble that travels down the chute? Use what you know about the conservation of momentum to describe what is happening.
4. What happened when you sent two marbles down the chute?
5. Write down the total momentum for two marbles of mass m both moving at velocity v. What is the kinetic energy of the system?
6. When you drop two balls at once, why doesn’t only one marble come off the end twice as fast? Write down the kinetic energy of one marble with mass m and velocity 2v and compare this to your answer in Question 4 to check. (Note that we are assuming the collisions are perfectly elastic, when in reality this is an approximation.)
Based on your results from the egg experiment, please answer the following questions:
1. Did you come up with a design that prevents the egg from breaking? Describe your approach in detail.
2. Why did adding layers of paper work better than one thick layer with the same number of sheets? (Hint: over how much time is the force applied in each case?)
3. What did you do to improve your apparatus?
4. Explain how a circus net prevents trapeze artists from injuring themselves even after falling from a large height.
5. Why it is important to bend your knees when you hit the ground after jumping from several feet in the air?