Screws

  A screw is simply an inclined plane that is wrapped around a cylinder or a cone. The main purpose is to raise a load over the threads, which is the spiral part of the screw, by applying a small force.

Screw vs. Nail Activity

*Complete the experiment following your Record Sheet, directions also appear below*

Purpose:

 Which takes less force to drive into an object, a screw or a nail?

Predictions: 

With your group, predict whether it will take less force to insert a screw or a nail into a bar of soap. Also predict which effort will take the most time and give reasons for your predictions.

Materials: 

               bar of soap (per group)

               glove

               a nail and a screw

Procedure:

               1. Push the nail into the bar of soap.

               2. Try to push the screw into the bar of soap. After the screw is in the soap, hold the screw between your thumb and index finger and turn it into the soap. Stop turning the screw when it is even with the nail.

               3. Try to pull the nail out of the soap. Now try to pull the screw out of the soap.

Observations:

                What happened when you pushed the nail into the soap?

                What happened when you tried to push the screw into the soap?

                What happened when you turned the screw?

Conclusions:

              Did the nail or the screw require less force to be inserted into the soap?

          Which of the following statements applies to the screw?

                   *It took less force to push it into the soap because the force was applied over a shorter distance.

                   *It took less force, but the force was applied over a greater distance. 

              A simple machine makes work easier. In this experiment, what work was done? 

Use the website below to help you answer your Conclusion Questions:

http://www.historyforkids.org/scienceforkids/physics/machines/screw.htm