Conservation of Momentum

Transcription

1 4.19 (page1) Conservation of Momentum When 5 students are standing in a row and someone pushes the first one, why does the last one fall down? In this experiment you will learn how momentum effects objects. A moving object is said to have momentum. Momentum is the mass of a moving object times its speed. A heavy object, moving at the same speed as a light object, will have greater momentum. For example, if a large truck and a small car are traveling at the same speed, it will take the truck longer to stop than the car. Because the truck is heavier, the truck s momentum carries it farther down the road. Momentum can also be transferred from one object or group of objects to another. In the game of pool, the cue ball transfers its momentum to the ball it hits and causes it to move. If the cue ball hits more than one ball, then the group of balls move. The group of balls has the same amount of momentum as the cue ball. momentum Words to Know Safety Precautions Please click on the whistle to view the safety guidelines.

2 4.19 (page 2) Science Projects For ALL Students WHAT YOU NEED 2 Hot Wheels tracks (straight) Play-Doh WHAT YOU NEED 2 inch block 6 plastic golf balls tennis ball WHAT YOU DO PREPARING THE RAMP 1. Place a small piece of Play-Doh under each end of both Hot Wheels tracks. 2. Place the end of 1 track on the block. Press down to secure the Hot Wheels track to the block. 3. Press the other end of that Hot Wheels track onto the table. This track is your RAMP. 4. Place the second track at the bottom of your ramp. Press down to secure it to the table. This is your TRACK. ACTIVITY 1. Place 4 golf balls in the middle of the track. Make sure that all the balls are touching. 2. Predict how many balls will move on the track once a ball from the ramp strikes them. Enter your prediction in the data table next to Trial Hold 1 golf ball at the top of your ramp. Release the ball. Be careful not to push it. Record the 1998 Facts On File, Inc. Published by Facts On File, Inc.

3 4.19 (page 3) number of balls moved in the data table. 4. Repeat steps 1 through 3 using the ball arrangements listed in the data table. OBSERVATIONS 1. What happened when you rolled 1 golf ball into the 4 on the track? 2. What happened when you rolled 2 golf balls into the 4 on the track? 3. What happened when you rolled the golf ball into the tennis ball? 4. Using the definition momentum = mass x speed explain your answers to questions 1 through 3. OUR FINDINGS Click on the above link to see what we found.

4 4.19 (page 4) 1998 Facts On File, Inc. CONSERVATION OF MOMENTUM DATA TABLE Trial Number of Balls on Ramp Number of Balls on Track Prediction: Number of Balls Moved Actual Movement 1 1 golf ball 4 golf balls 2 2 golf balls 4 golf balls Published by Facts On File, Inc. 3 1 golf ball 1 tennis ball Science Projects For ALL Students

5 Our Findings 4. PHYSICAL SCIENCES 4.19 CONSERVATION OF MOMENTUM 1. The golf ball from the ramp stopped after it collided with the other balls. One golf ball from the opposite end moved down the track. 2. Two golf balls moved down the track. 3. The golf ball stopped and the tennis ball moved off slowly. 4. In trials 1 and 2, the balls that moved off the track had the same mass and about the same speed as those that hit them, as the law predicts. In the case of the golf ball hitting the tennis ball, the tennis ball had more mass than the golf ball. Since the law of conservation of momentum predicts that the total momentum among all the balls will remain the same, the tennis ball, with more mass, will have to move with less speed than the golf ball, with less mass, that collided with it.

6 SAFETY GUIDELINES Special Safety Note To Experimenters Some activities in this book have special safety rules to follow. The special rules are on the page with that activity. But even if every safety rule in the world is included with an experiment, you have to know how to be safe when doing it. So it s very important that you read, copy, and follow the Everyday Safety Rules that follow. Sometimes science experiments can be dangerous. Things can spill, break, or even catch fire. You have to know what to do... fast. So be prepared. Read the directions for each experiment carefully, and follow any special safety rules listed with it, then be careful. Always follow common-sense safety rules like NEVER RUN WITH SCISSORS IN YOUR HAND or BE CAREFUL WITH HOT THINGS! You already know a lot of common-sense safety rules... so remember to follow them, and have fun! Everyday Safety Rules PREPARE Clear off your work space. Read all directions. Know what problems might happen, and be prepared. PROTECT YOURSELF Follow directions step-by-step. Do just one experiment at a time. Locate exits, fire extinguisher, eye wash, and first-aid kit before you start. Ask an adult to show you how to use a fire extinguisher. Be sure there s fresh air in the room. Wear an apron and safety goggles. Don t wear contact lenses, have bare feet, or wear very loose clothing. Keep work space and floor clean. Clean up spills immediately,

7 Don t drink or eat around the experiment work space. Don t eat or drink any stuff tested, unless a grown-up says it s OK. USE EQUIPMENT CAREFULLY Don t set up equipment too near the edge of your work space. Be cautious when using pointed or sharp instruments, like scissors, screwdrivers, or knives. Unplug any electric device by pulling out the plug, not pulling on the cord. Use only low-voltage batteries, like those used in flashlights or smaller. Be careful when using chairs or step-stools. USING CHEMICALS Have an adult help you with all experiments requiring chemicals. Don t inhale or taste chemicals. Read all labels carefully. Label all chemicals. Wear goggles, apron, and gloves so chemicals don t touch your skin. Wash hands before and after using solutions. Wipe up spills thoroughly. HEATING THINGS Wear goggles, apron, and gloves when boiling water. Use safety tongs and heat-resistant mitten or hot pads. Never leave heated things unattended. Turn off hot plates and oven burners when you re finished. Keep flammable things away from heat and flames. Have a fire extinguisher ready. IN THE FIELD Never go on a field trip alone: follow the Buddy System. Tell a responsible grown-up where you re going. Know the area and be aware of dangers, like poisonous plants and deep water Dress for the weather conditions.