Some of the machines you use every day are made up of several simple machines. Two or more simple machines that operate together form a compound machine.
Look at the can opener in Figure 1.
Compound machine – a can opener
To open the can, you first squeeze the handles together. The handles act as levers and increase the force applied on a wedge, which then pierces the can.
You then turn the handle, a wheel & axle, to open the can.
Thus the can opener is made up of multiple simple machines. That’s why a can opener can be called a compound machine.
A car is a compound machine
Burning fuel in the cylinders of the engine causes the pistons to move up and down. This up-and-down motion makes the crankshaft rotate.
The force exerted by the rotating crankshaft is transmitted to the wheels through other parts of the car, such as the transmission and the differential.
Both of these parts contain gears that can change the rate at which the wheels rotate, the force exerted by the wheels, and even reverse the direction of rotation.
Hence, A car is a compound machine.