Force and Energy
Concept: Simple Machines and Levers
What is a machine?
A device used to make our work easier is called a simple machine.
Features of a simple machine:
- Simple machines are made of minimum moving parts.
- The most useful simple machines are levers, wheel and axle, pulleys, inclined planes, screws and wedges.
- All complicated machines we use in our day-to-day lives are assembled using these simple machines.
- Machines decrease the level of human effort and time required to do any task.
Types of simple machines:
- Wheel and Axle:
- Early man invented the wheel for revolutionizing transport.
- Wheel, when combined with a rod-like structure called axle, makes a simple machine.
- Wheel and axle are used in bicycles, cars, motorcycles, sewing machines, potter’s wheels, egg beaters, gears, windmills, doorknobs, steering wheels etc.
- A grooved wheel that allows the rope to pass on its surface is called a pulley. It is a circular structure that rotates freely on its axis, aiding the movement of a rope, belt or chain.
- A pulley can be used to both pull down and pull up the load.
- Pulleys can be of two types—fixed pulleys and movable pulleys.
- Fixed pulley: The pulley is attached to a fixed position with a rope attached to it. A fixed pulley is used in flag poles and sail masts.
- Movable pulley: In this case, the pulley is free to move up and down and is attached to a ceiling or other object by two lengths of the same rope. A movable pulley is used in construction cranes, elevators, and weight lifting machines.
- It is the flat inclined surface used to move or raise heavy objects.
- It helps in lifting the load with less force.
- The force required to move an object on an inclined plane increases with an increase in the distance of the inclination
- Inclined planes are used as ramps for wheelchairs and for loading luggage in trucks.
- A wedge is an object that tapers to a thin edge, basically used for cutting. A double wedge is used by attaching two inclined planes. A wedge is an object that tapers to a thin edge, basically used for cutting. A double wedge is used by attaching two inclined planes.
- Wedges are used to make cutting tools like a chisel, axe, plough blade, and the bow of a boat or a ship.
- The screw resembles an inclined plane wrapped around a cylindrical structure.
- The inclined plane is shaped to form ridges and spirals along the cylinder. These ridges and spirals are called threads of the screw.
- The pitch of a screw is defined as the distance between the thread of a screw.
- The screw is used to hold things together. The spirals of the screw enable it to go deeper and hold things stronger.
- Screws are used to put the small parts of a complex machine together, and the bases of the bulbs are screw-like structures.
- Screws can be seen in pen caps and bottle caps too.
- One can understand a lever based on three things—fulcrum, load and effort.
- An effort is defined as the downward force applied.
- The balance point of the lever is the fulcrum, and it does not move.
- The force applied depends on the position of the fulcrum.
- If the fulcrum lies closer to the load, the force required to lift the load is less.
- If the fulcrum lies closer to the effort, then the force required to lift the load will be more.
Types of levers:
- Class-I lever:The lever where the fulcrum lies in the centre of the load and the effort.
- Class-II lever:It is the lever where the load lies between the effort and the fulcrum. The position of the fulcrum is closer to the load, which decreases the force required to accomplish the work.
- Class-III lever:It is the lever where the effort lies between the load and the fulcrum. This arrangement helps in the movement of load for long distances with less force.
Plier, scissors, water pump, crowbar.
Wheelbarrow, nutcracker, bottle opener.
Fishing pole, tweezers, callipers, the person holding a hockey stick, and a spade.
Chisel: A hand tool with a long blade used for cutting and shaping wood, metals and stones..
Assembled: Fitting together the individual parts to make something, like a machine.
Did You Know?
- Scissor is a wedge combined with a first-class lever and hence, can be considered a complex machine.
- A see-saw is a regular fixture at playgrounds and uses the power of a class-I lever.
- A wheel and axle is a first-class lever where the axle is placed instead of the fulcrum, and arms are fixed around the axle to make a disc of the wheel.