Newton's Cradle V5 - Community Science Workshop · PDF fileScientific"progress"is"made"by"asking"meaningful"questions"and ... 3.2"Note"the"method"of"deriving"the"solution"and"demonstrate"a

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Newton’s Cradle

Category: Physics: Force & Motion, Balance & Center of Mass, Waves & Vibrations

Type: Make & Take Rough Parts List:

Video: http://youtu.be/r7TVvXE1e8g

How To:

Glue 2 craft sticks into a “T”. Do this twice to make two T’s.

Attach a “T” on two sides of the baseboard. Line them up the best you can.

10 Binder clips 5 Marbles, 1” diameter works well 4 Large craft sticks or paint paddles 2 Wood blocks, 1x2 x 3.5” 1 Baseboard, 2x4 String, kite Super glue


Cut the two wood blocks so that

they fit tightly between the two T’s.

Attach a wood block between

each end of the two T’s.

Measure a piece of string so that

it is twice the length of a craft stick. Cut 4 more pieces of string the same length as the first.

Make dents for the marbles to sit in. Put a blob of hot glue onto each marble and press the center of each string into the hot glue.

Allow the glue to cool and set then peel it off the marble. Attach the dried glue to each

marble with super glue. Gel type works best.


Find and mark the center of each T.

Measure 2 more marks on each side of the center mark placing them 1”apart: the

diameter of the marbles.

Hang the marbles by clipping both ends of string to the top of the T.

Align the string so the marble is centered and hangs just above the baseboard.

Adjust the marbles by pulling on the strings and moving the clips until they are all exactly the same height and in a straight line. They should be bearly touching, not leaning hard on

each other. Try it out.

Fine Points: → Adjustment takes a long time to get right. You are adjusting the balls’ positions in 3D space, and it has

to be right in all dimensions. → Try letting it go after pulling two or three or four off to one side as well as just one. → Pull one back from each side and let them fall the same time. Try it again letting them fall at slightly

different times. → You can make it with as many balls as you want. Five balls makes it interesting without too much

complexity.


Concepts Involved: • Momentum is conserved. In a collision the sum of each mass times its velocity before the collision

will equal the sum of each mass times its velocity after the collision. One marble hitting the group sends another marble up at the same speed since their masses are the same.

• Collisions come in two forms: elastic and inelastic. The glass in the marbles is highly elastic which means that when they collide, the marbles do not stick together.

• The force from the marble hitting travels through the other marbles with a shock wave. The wave delivers all the force and energy necessary to send the marble up at the other end.

Focus Questions: 1. What happens if you pull back all but one marble and let them go? 2. What happens if you pull back one marble from each end and let them go at the same time? 3. What happens if you put a tiny piece of chewed gum between two of the balls and then let one

drop? Move the gum to a different marble and try it again. 4. What happens if a car hits a parked car of exactly the same size?

Elaboration: Momentum is related to mass and speed. When two things hit each other, you can see the effects of momentum. There are two ways things can hit each other: They can stick together, or they can bounce off each other. In this project, they will bounce off each other. You probably already have a gut understanding of momentum. If a small person runs into a big person, the big person will not move much. But if a big person runs into a small person, the small person will move a lot. In this project, the balls are all the same size, so you can see what happens more easily. This project demonstrates the principle of conservation of momentum. This principle states that momentum is never lost, but rather transfers from one place to another. Momentum is defined as an object’s mass multiplied by its velocity. When a single marble is dropped, it accelerates downward until it hits the other marbles. When it hits the marbles, it has a certain velocity. After it hits that marble, it comes to a complete stop. For momentum to be conserved, something else with the same mass should take off at the same velocity in the same direction. You can see that happen with the marble on the other end. With two marbles, the mass has doubled, and two marbles will take off from the other side. Drop three and there are not three separate marbles to go up so one of the ones dropped must continue. Drop four and only one will remain stationary. It is hard to measure the velocity of marbles in this project, but velocities can be compared by watching how far up the marble swings. The higher the marble swings up, the larger velocity it had when it first began swinging. If you drop a marble from a higher position, the one that swings up from the other end should also swing up to a higher position. The force from the marble hitting one side travels through the other marbles in the form of a shock wave. If you use only two marbles, and put a piece of gum or clay on one marble, it will absorb the shock wave when it hits. It will also connect the two so they’ll move together. When they’re together, the mass is double. When the mass doubles, the velocity should half, so they should swing up to a lower height than the one was dropped


from. You can also try the gum experiment with the whole line, which will raise the mass by five times, so the height they rebout to should drop a lot. This project is called Newton’s Cradle because it looks like a cradle when it’s moving and because Isaac Newton made many breakthroughs in understanding force, energy and momentum.

Links to k-‐12 California Content Standards: Grades k-‐8 Standard Set Investigation and Experimentation Scientific progress is made by asking meaningful questions and conducting careful investigations. As a basis for understanding this concept and addressing the content in the other strands, students should develop their own questions and perform investigations. Grades k-‐12 Mathematical Reasoning: 1.0 Students make decisions about how to approach problems: 1.1 Analyze problems by identifying relationships, distinguishing relevant from irrelevant information,

sequencing and prioritizing information, and observing patterns. 1.2 Determine when and how to break a problem into simpler parts. 2.0 Students use strategies, skills, and concepts in finding solutions: 2.1 Use estimation to verify the reasonableness of calculated results. 2.2 Apply strategies and results from simpler problems to more complex problems. 2.3 Use a variety of methods, such as words, numbers, symbols, charts, graphs, tables, diagrams, and

models, to explain mathematical reasoning. 2.5 Indicate the relative advantages of exact and approximate solutions to problems and give answers to

a specified degree of accuracy. 3.0 Students move beyond a particular problem by generalizing to other situations: 3.1 Evaluate the reasonableness of the solution in the context of the original situation. 3.2 Note the method of deriving the solution and demonstrate a conceptual understanding of the

derivation by solving similar problems. 3.3 Develop generalizations of the results obtained and apply them in other circumstances. Grade 2 Standard Set 1. Physical Sciences: The motion of objects can be observed and measured. 1.c Students know the way to change how something is moving is by giving it a push or a pull. The size of

the change is related to the strength, or the amount of force, of the push or pull. Grade 3 Standard Set 1. Physical Sciences (Energy & Matter): 1.d Students know energy can be carried from one place to another by waves, such as water waves and

sound waves, by electric current, and by moving objects. Grade 8 Standard Set 2. Forces: Unbalanced forces cause changes in velocity. 2.e Students know that when the forces on an object are unbalanced, the object will change its velocity (that is, it will speed up, slow down, or change direction). Grade 9-‐12 Physics Standard Set 1. Motion & Forces Newton’s laws predict the motion of most objects.


1.b Students know that when forces are balanced, no acceleration occurs; thus an object continues to move at a constant speed or stays at rest (Newton’s First Law).

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Newton's Cradle V5 - Community Science Workshop · PDF fileScientific"progress"is"made"by"asking"meaningful"questions"and ... 3.2"Note"the"method"of"deriving"the"solution"and"demonstrate"a