Force is anything that causes a change in motion. Newton realized that the force applied must be greater than the resistance of an object to cause movement. To measure the distance caused by a force we use meters. Ask ALL children to describe the direction in which it falls. Work is done when a force moves something.
Gravity is a force which acts upon objects and systems.
A pendulum is a system which can be used as a timing device such as in a clock. We can use it to investigate the relationship of forces acting upon objects in motion. Cut lengths of string. Collect data on the number of swings a pendulum makes in 10 seconds. Predict the number of swings the pendulum will make in 10 seconds.