There are basically two types of motion - LINEAR (in a straight line) and (ROTARY (in an arc or circle).
These two types of motion can be split again into RECIPROCATING (Linear going backwards and forwards) and OSCILLATING (Rotary going backwards and forwards in an arc).
Sliding doors are an excellent example of RECIPROCATING MOTION.
The pendulum on a clock is a good example of OSCILLATING MOTION whilst the hands on the clock demonstrate ROTARY MOTION.
In many cases the two kinds of motion are interconnected. In the car engine RECIPROCATING MOTION (the pistons going up and down) is converted to ROTARY MOTION (the crankshaft going round and round).
In the case of a Mechanical Hacksaw the ROTARY MOTION of the electric motor is converted into the RECIPROCATING MOTION of the saw going backwards and forwards to cut the metal.
A SCREW THREAD is an excellent example of converting ROTARY MOTION into LINEAR MOTION and this principle is used on many objects. On a Car Jack, for example, you use ROTARY MOTION to lift the car up (LINEAR MOTION).
The RACK & PINION is another way of changing ROTARY MOTION into LINEAR MOTION and examples of this to be found in the school workshop are on the Drilling Machine and on the Mortising Machine.
When you pull the handle down on the Drilling and Mortising Machines the drill or the chisel moves down.