Download Lesson 6 Newton`s Law Pt 2

Newton 1:
Half-fill the mug with water and pour in some vegetable oil so that it forms a thin
layer on the surface of the water. Place a couple of drops of food colouring on
top. Hold the mug as shown and quickly twist your wrist to turn the mug through
90◦. The mug moves because you exerted a force on it, but the food colouring
stays in the same place because you did not exert much of a force on the liquids.
Newton 2: Light Gate and Datalogger Method
A description of the standard experiment
using light gates is available from:
www.schoolphysics.co.uk/.../newton's_second_law_air_track.doc
Newton 2: Mountain Boarding
Materials:
Mountain board
Cycle helmet, elbow and knee pads
Newton balance
Tape measure
Stopclock
Rope
Scales
Directions:
Place the mountain board on a slope and check that it is friction compensated i.e. the weight
balances the force of friction. (When given a push, the student should travel at a steady speed.)
Attach a rope to the student and ask a volunteer to pull it with the dynamometer. By running,
they should try to maintain a steady force reading on the dynamometer. Starting from rest,
they should pull the student over a known distance whilst the time is taken. Repeat to check
reliability of results. Use the scales to find the mass of the student. Ask students to find the
acceleration using NII and by considering the rate if change of velocity. Discuss how the two
figures compare.
Example Results
Distance = 20 m
Time taken = 10 s
Average accelerating force = 40 N
Mass of rider and board: 50 kg
Initial speed = 0 m/s and so final must be double the average speed. So the final speed = 4 m/ s
Newton 3: Skateboards and Toy Poppers
Ask a volunteer on a skateboard to push a wall. Discuss his motion in terms of Newton’s 3rd
Law. The behaviour of toy poppers can also be included. You might want to mention that
squids propel themselves forwards by filling their bodies with water and ejecting it
backwards. You could also discuss gun recoil.
Newton3: Balloon Rocket
String/ Fishing Line to act as a track for the rocket
5 cm length of a drinking straw
Balloon
Thin card
sellotape
Directions:
Thread the string through the straw. Attach the string to two clamps making sure it is taut
and level. Blow up the balloon and attach it to the straw with cellotape and let go. Discuss
what would happen if you repeated the experiment with a balloon filled with helium. Balloon
helicopters can also be used to demonstrate this. They can be bought for 3 dollars from
http://www.arborsci.com/SearchResult.aspx?CategoryID=12
Newton 3: Stomp Rocket
Attach plumbing pipes together and
secure to a wooden board. Place a
paper rocket on one end and an empty
fizzy drinks bottle to the other
Jump
on the
bottle.
Newton 3: Alka-Seltzer Rocket
The following website describes how to build Alka-Seltzer rockets:
http://scu.uwe.ac.uk/PDFs/ZeroCarbonCity_demonstrations.pdf
It then relates how the rockets work to the carbon cycle, likening the production of gaseous
CO2 from the solid tablets to the release of CO2 into the atmosphere from burning fossil
fuels.
Newton 3: Water Rocket
Kits which turn an ordinary fizzy drinks bottle into a rocket can be bought from:
http://www.rokit.com/products.asp
Newton 3: Diet Coke and Mentos
Diet coke is a liquid which is supersaturated with carbon dioxide gas. A nucleation site is a
place where the gas is able to form bubbles. Nucleation sites can be scratches on a surface or
specks of dust – anywhere that you have a high surface area in a very small volume. That’s
where bubbles can form. The surface of a Mento has lots of nucleation sites i.e. there are
many microscopic nooks and crannies on to which an incredible number of bubbles will form
when you drop it in a bottle of soda. Since the Mentos are also heavy enough to sink, they
react with the soda all the way to the bottom. The escaping bubbles quickly turn into a foam
and the pressure builds dramatically, forming a geyser. This experiment can be
adapted to demonstrate Newton’s Third Law.
http://www.wikihow.com/Make-a-Diet-Coke-and-Mentos-Rocket
http://www.stevespangler.com/archives/category/mentos-experiment/