# Plasticine

#### Introduction

Plasticine is a sort of plastic modelling clay but you could also use play dough which can be made out of flour oil and salt like this:

2 cups flour
2 cups warm water
1 cup salt
2 Tablespoons vegetable oil
1 Tablespoon cream of tartar

Mix it all together put it in a saucepan then stir over a low heat until it resembles mashed potato then allow to cool and knead on a clean surface until smooth.

Plasticine was the first "design" experiment I ever did and I have used it many times with different classes, I'm getting a bit bored of it now so have graduated to potty putty which is a bit more interesting. If you can get hold of conductive putty then this could have even more possibilities.

#### Research questions

1. If you push a pencil into the Plasticine it makes a hole,

What is the relationship between the depth of hole and the force applied to the pencil?

Independent variable: Force applied to pencil

Dependent Variable: Depth of hole

Controlled variables:

Diameter of pencil
Angle of attack
Temperature of plasticine
Size and type of plasticine

Rough method

A cube of plasticine is placed on the table and a pencil is arranged above in a guide tube as shown in the diagram. This tube will keep the pencil vertical. A vertical ruler is used to measure the top of the pencil. Weights are now added to the ruler causing it to push into the plasticine, as this happens the top of the pencil is measured to give the depth of indentation.

2. Again pushing a pencil into the Plasticine

What is the relationship between the depth of hole and the velocity of the pencil?

Independent variable: Velocity of pencil

Dependent variable: Depth of hole

Controlled variables:

Diameter of pencil
Angle of attack
Temperature of plasticine
Size and type of plasticine

Mass of pencil and anything attached

Rough Method

This time the pencil is mounted on a cart which is sent down a track to collide with the cube of plasticine, the velocity of the cart is measured using a photogate that records the time taken for a card attached to the cart to pass. The velocity of the cart is varied by pushing it along the horizontal track with different amounts of force. The size of hole made in the plasticine is measured using the spike on a vernier calliper. After each run the cube is reformed.

3. A ball of plasticine will exert a force on the floor if dropped

What is the relationship between the maximum force and the temperature of the plasticine?

Independent variable: Temperature

Dependent variable: Maximum Force

Controlled variables:
Distance fallen
Size of ball (volume, mass etc.)
Type of Plasticine

Rough Method

Since the force changes so quickly, to measure the maximum force a digital force sensor will be require. Pasco make a platform to fir on the sensor or you can make your own. The plasticine ball can then be dropped onto the platform and the force recorded. To vary the temperature a water bath could be used however the plasticine gets very soft so it might be better to use go below room temp in a fridge. the temperature can be measured by inserting a thermometer into the plasticine.

4. When a ball is dropped on the floor the side that lands on the floor becomes flat.

What is the relationship between the diameter of the flat bit and the height it falls from?

Independent variable: The height of the fall

dependent variable: The diameter of the flat

Controlled variables

Size of ball (diameter, mass)
The type of plasticine
The temperature if the plasticine

Rough Method

This one doesn't require anything fancy just a ruler to measure the drop height and a ruler or vernier calliper to measure the diameter of the flat bit. Attention should be given to forming the ball into the same shape without increasing the temp.

5. You can make a plasticine sausage by rolling a cylinder between two books

What is the relationship between the length of sausage and the distance rolled?

Independent Variable: The distance rolled

Dependent Variable: The length of the sausage

Controlled Variables:

The force applied between the books
The temperature of the plasticine
The type of plasticine
The starting size of the cylinder

Rough Method

This one can also be performed with just rulers. the difficult part is going to be keeping the force constant and measuring how far the sausage is rolled. This can be found by measuring the distance moved by the top book (backwards and forwards) as the rolling progresses the temp is likely to increase so should be done slowly. The length of sausage can be measured at regular intervals by taking off the top book and using a ruler, the sausage may need to be straightened out from time to time.

6. when you squash a cube of plasticine on the table the area of its top surface gets bigger

What is the relationship between the area of a cube and the force exerted on top of it?

7. You can make discs with plasticine and drop them onto the floor, as they fall the air resistance will affect their motion.

What is the relationship between the area of a disc and its average velocity whilst falling a fixed distance?

8. A simple Newtons cradle can be made out of string and two balls of plasticine, when one ball hits the other the collision is inelastic.

What is the relationship between the distance one ball is lifted and the height the second ball rises to?

9. If a cylinder of plasticine is put on the table and pushed downwards it will become shorter.

What is the relationship between the force needed to deform a cylinder by 5mm and the diameter of the cylinder?

10. Cylinders of plasticine can be rolled down an inclined plane.

What is the relationship between the time taken for a cylinder to roll down a slope and the diameter of the cylinder?

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