Force and motion
A world without machinescan be tough to move heavy stuff.
A world without machines would be tough because you would have to push and pull heavy stuff without them
You might know one machine whitch is known as the teeter toter That is one machine that is a lever because when you are balanced with your friend on a teeter toter you are able to push your friend up on it and you go down then then when you push your feet off the ground you go up and your friend goes down. If your friend is sitting on the end and you are trying to push it down from the middle it will be tougher because you are't ballenced with your friend on the teeter toter.
Another Machine is a knife and that is a lever because you have to push on it for it to cut the food or what you are trying to cut. A knife can cut hard things like peppers because a knife is also a wedge and a wedge is something that you can cut into two pieces or in half if you want it cut in half. It can also cut chicken because it would be hard to cut chicken with a fork.
The last one I have is the screw which is a screw because it is an inclined plane that is warped around a cylinder. A screw go's in a circle motion when it is going in the wall or in anything else when you need it.