Everything Science Grade 11

CHAPTER 12. FORCE,MOMENTUM AND IMPULSE 12.3

Step 3 : Name the action-reaction pairs

The question only asks for action-reaction forcesin the horizontal plane.There-

fore:

Pair 1: Action: Appliedforce of the girl on the book; Reaction: The force of the

book on the girl.

Pair 2: Action: Force ofthe book on the wall; Reaction: Force of the wall on the

book.

Note that a Newton III pair will always involve the same combination of words,

like ’book on wall’ and’wall on book’. The objects are ’swapped around’ in

naming the pairs.

General experiment: Balloon Rocket

Aim: In this experiment for the entire class, youwill use a balloon rocket to investigate

Newton’s Third Law. Afishing line will be usedas a track and a plasticstraw taped to the

balloon will help attachthe balloon to the track.

Apparatus: You will need the following items for this experiment:

1. balloons (one for each team)


2. plastic straws (one for each team)


3. tape (cellophane or masking)


4. fishing line, 10 meters in length


5. a stopwatch - optional (a cell phone can alsobe used)


6. a measuring tape - optional

Method:

1. Divide into groups of at least five.


2. Attach one end of thefishing line to the blackboard with tape. Have one teammate hold
   the other end of the fishing line so that it is tautand roughly horizontal.The line must
   be held steady and must not be moved up or down during the experiment.


3. Have one teammateblow up a balloon andhold it shut with his orher fingers. Have
   another teammate tapethe straw along the sideof the balloon. Threadthe fishing line
   through the straw and hold the balloon at the far end of the line.


4. Let go of the rocket and observe how the rocket moves forward.


5. Optionally, the rockets of each group can betimed to determine a winner of the fastest
   rocket.

(a) Assign one teammate to time the event. The balloon should be letgo when the

time keeper yells “Go!”Observe how your rocket moves toward the blackboard.

(b) Have another teammate stand right next to the blackboard and yell “Stop!” when

the rocket hits its target. If the balloon does not make it all the way tothe black-

board, “Stop!” should be called when the balloon stops moving. The timekeeper

should record the flighttime.