Vedavalli Vidyalaya, Walajapet, Tamil Nadu
Class V C & V D, August – September 2017

Small Science – Class 5
Chapter 3 – How things move

Sliding, rolling, slipping

I as a science teacher of Class V would love to share my experience in teaching the topic of friction – rolling and sliding – in the Chapter, “How things move”.

I divided the children into five groups and gave each group a cardboard writing pad, which was smooth on one side and rough on the other. I asked them to tilt the writing pad by raising one end and to slide down it a few things like a coin, eraser, sharpner, pencil and bottle cap. They did the sliding on both sides of the writing pads. Then we spread boric powder on the surfaces and repeated the same activity. We compared how much the surfaces had to be raised for the objects to begin sliding. The children noticed that some objects slid easier than others. The sharpner slid easier than the rubber. The smooth cardboard surface with the boric powder on it had to be tilted the least and the rough surface without powder had to be tilted the most for the objects to begin sliding. For the four different sliding surfaces the friction between surface and objects was different. Then children then did the same activity with three different rulers made of iron, plastic and wood, with powder and without powder. They tilted the rulers to different heights to slide the different objects. Thus they got rich and varied experiences of varying frictional forces.

From this activity, the children tried to answer, “Think! Think!” TextBook pg:42, “Why did putting talcum powder make the coin slide easily?” All the children said that boric powder had made the surface smooth, so the coin slid easily. At first they could not say in an elaborate way that the powder helped to fill the valleys between bumps, causing the objects to move on a thin layer of the lubricant, with less friction. I repeated the experiment applying boric powder on the rough surface of the writing pad and asked them to roll a toy wheel and watch keenly the surface of the writing pad and the surface of the wheel. Some children said that the powder occupied the small “holes” (valleys between the bumps) in the pad and wheel, so the surface became smooth. From this activity the children could understand that, the powder fills the valleys and makes the surface smooth.

To add interest I did an activity using a carrom board. The children played carrom without powder. They found it difficult to strike the coins and they noticed that the coins did not slide easily. When they spread the powder they found it easy and noticed that the coins slid because of less friction.

Wheels made of rubber / nylon

The children observed different tyres of cars, buses, scooters and bicycles in the school ground and noticed that their tyres are not smooth, but treaded. Back in the classroom we started the discussion by, what would happen if the car tyre was made of metals? I got different answers from the children:

> the metal tyre cannot move easily on stones
> it cannot climb on mountains
> we get an irritating sound when the tyre hits on stones
> often the tyre shape gets damaged
> we cannot stop the car suddenly when we put the brake
> the shape of the tyre changes permanently

From these responses it seems children understand intuitively that metal tyres would be heavy so could not move easily, and also they would not bounce back to their original shape like rubber or nylon tyres. Children also realised that rubber tyres are easier to stop after applying brakes. We have to help them link this intuition with new concepts.

The interesting concept here is that rolling is possible only if the surface of the wheel does not slip and slide on the surface of the road. So rolling needs a high friction between the two surfaces. The next activity was meant to clarify these ideas.

Friction and rolling

We used thalis to observe friction in rolling. Children bought to class bobbins, bottle caps, old toy wheels, beads and small balls. They were divided into groups and 2 thalis was given to each group, one dry and one covered with soapy paste. Children started to roll the objects on the thalis using twigs, pen refills and some children used their hands to roll. They experienced different movements like rolling, sliding, slipping, slow, fast and also differences between rough and smooth surfaces.

The workbook responses showed that children observed that the soapy paste reduces friction and makes the wheels slide. Also the rubber ball continued to roll in the soapy water, though not so well, but the bobbin, bottle cap and toy wheel tended to slip. It may take time for children to assimilate all these results and draw conclusions from them.

We have to discuss how the treads of tyres help in increasing friction and also helping the wheels roll on wet slippery roads. When the wheels press down on a wet road the water is expelled from between the treads, thus friction is increased and the wheels roll easily again.

How to make things move

We did this activity in classroom as well as in the corridor. Since the rolling of the ball was not visible to all the children inside the classroom, I made them sit in the corrider in two parallel lines. I told the children to roll the ball from one end and then slow down the rolling ball without touching it. One child started to roll the ball, the others immediately threw a shawl, books, pencils, sharpners and handkerchiefs to make the ball slow down. I gave a chance to all the children to roll the ball. At last, all the children gathered their books at one place on the way, covered with their handkerchiefs and they kept one box like an elevation. The ball hit on the elevation and started to move back slowly. Also later the children tried different ways to make the ball roll in straight line.

In a nutshell, the concepts in the chapter, “How things move” are easier to understand through interesting activities as mentioned in Small Science. Though there are many challenging ideas still to come, I feel that their experiential learning will stay with them in the future.