Today’s topic of focus is friction.
Here are some things sixth graders are expected to know:
- it’s a force that exists between surfaces that are rubbing against each other
- acts in the direction opposite to the direction of motion
- acts to reduce the speed of a moving object
- we rub our hands together for warmth because the friction between our palms produces heat
- this is why it is possible to rub two dry pieces of wood together to make fire. The friction between the two pieces produces enough heat to spark a flame
- friction between rougher surfaces is greater and produces more heat than friction between smoother surfaces
- friction between the soles of our shoes and the ground allows us to walk and run without falling. Putting grooves (or threads) on the soles of shoes increases the friction between the shoes and the ground
- friction between tyres and roads allows vehicles to slow down and come to a stop when brakes are applied
- Friction causes wear and tear. The soles of shoes wear out. This decreases the grip of shoes on surfaces and may result in slipping on wet surfaces. Tyres also become smoother over time, thus causing a vehicle to slip on wet surfaces
- Friction makes things overheat and causes objects to move slowly. Hence, machines work less efficiently.
- Lubricants like oil, grease, wax are applied on moving parts of machines and door hinges. This smoothens the surface to reduce friction so that the lubricated parts can move more easily against each other
- Rollers, wheels and bar bearings are used on conveyor belts, bridges and trolleys so that friction is reduced between moving parts, thus enabling easier movement
- Cars, planes, ships, water surfing boards and rockers are streamlined to reduce friction with air or water. This makes them move faster because the surface area that encounters air or water resistance is reduced, consequently reducing friction.
And three questions to apply your understanding, courtesy of Mendaki