# Activity 2 - More about contact forces

30 minutes

Discussions

## Prerequisites/Instructions, if any

Students must have been introduced to the Newton's laws.

## Process (How to do the activity)

1. This is in the nature of discussions
2. Present scenarios for children to analyse

## Developmental Questions (What discussion questions)

1. When you hang a bucket from a rope what are the forces acting? (Tension force is the force that is transmitted through a string, rope, cable or wire when it is pulled tight by forces from opposite ends. The tension force is directed along the length of the wire and pulls equally on the objects on the opposite ends of the wire.)
2. In which direction does tension act?
3. Is this the same as friction? When do you notice friction? (Frictional force is the force exerted by a surface as an object moves across it or makes an effort to move across it. When two objects are in contact but are not moving relative to one another then the frictional force between the two surfaces is called static friction. When the two objects are moving relative to one another, the friction between the surfaces is called the kinetic friction.)
4. When you push against an object, any surface, what do you feel? Do you feel a push back? Normal force is the perpendicular force that is exerted upon an object that is in contact with another stable object. If a book is resting upon a surface, then the surface is exerting an upward force upon the book in order to support the weight of the book. A normal force can also be exerted horizontally. If a person leans against a wall, the wall pushes back on the person.

## Evaluation (Questions for assessment of the child)

1. What do the moving green and yellow circles indicate?
2. When you are rubbing the yellow book on the green book what happens? How do you know that the heat is being generated?
3. When the temperature goes very high, the yellow circles fly off. What does this mean physically?
4. Is there any force acting in this picture between the books?
5. Is gravitational force acting?

1. Discussion