Throughout this guide, important keywords are in bold. Make sure you understand them. Words defined in the vocabulary section are in italics in the text.
Here is the list of the vocabulary used in this study guide.
Pivot: A central point around which something rotates.
Linear Motion: Movement along a straight line, that is, not a curved path.
Rotational Motion: Movement along a circular path.
Friction: A force,opposing motion, that exists whenever there is motion.
Load: The object that is required to be moved.
Input Force: The force applied by the person applying force.
The World Around Us
The world around us is highly mechanised. Each task in our world is carried out by a machine. But our ancestors weren’t like this. The machines that they used were very crude. And undoubtedly, the machines that we use today are built of the very same basic machines.
Simple Machines are the most basic machines that used to decrease the amount of force or the direction of force. Simple machines are machines that have few or no moving parts and are meant to make our life easier. For example, the pulley used to lift water from a well, a see-saw etc.
But how do these machines make our life simpler?
A task may require the application of a large force for a short distance. The force multiplied by the distance moved by the load is the work.
- The work required to accomplish a task remains the same, irrespective of how we do it.
- A simple machine reduces the force required to accomplish the work.
- But, it increases the distance it has to be applied for.
So, the work remains the same, but it is easier to do it. For example, lifting a heavy object directly would require much more force than pushing it over a slope. In pushing it over the slope, the load moves a larger distance.
Simple machines can also be used to change the direction of force applied. Like, in a see-saw when one person goes down, the person on the other arm is pushed up. So, the direction of force is changed from downwards to upwards. It would have been much more difficult to pull the person upward directly.
Simple Machines make our life simpler by decreasing the amount of force or the direction of the force applied. They thus provide a mechanical advantage.
Mechanical Advantage is the ratio of the force at the point of load exerted by a machine to the input force applied to it.
Types of Simple Machines
There are 6 Simple Machines. These are:
Pulley : Changes the direction of force
Screw : Converts rotational motion to linear motion
Lever : Moves around a pivot point to increase or decrease mechanical advantage.
Wheel and Axle : Reduces the force of friction by utilizing rotational motion
Inclined Plane : Makes it easier to lift objects
Wedge : Forces objects apart
All other machines are made out of combinations of these simple machines. Such machines are called compound machines.
This post is part of the series: Simple Machines Study Guides
The complete study guide on Simple Machines for 4th graders.