what is linear stepper motor and rotary stepper motor? any details or description for these?

A stepper motoris a motor that uses two or more electromagnetic pole assemblies with teeth on them such the teeth are are off set so you can get very precise movements base on which poles are energized.

There are two both linear and rotary steppers. Linear stepper motors are laid out in a linear configuration. Rotary steppers are similar to a conventional motor.

Which coupling is used for joing to shafts of different diameter.....?

There are a number of type of couplers which can be used to join shafts different diameters:

1.Spider Connectors - These connectors also allow for misalignment.

2. Straight connectors - With different hole diameters in each end.

Why is a "Cup Car" with a full tank of fuel faster than the same car with a half tank of fuel?

small adjustment can make a world of difference in performence pressure but with 2 identical car of same weight and same horsepower i would think that the power the power to weight ratio on the car with less fuel would be faster due to the pushing less weight

What is the process to measure the speed of aeroplane

The airspeed indicator is the only instrument connected to both the pitot tube and the static system. Air from the staticsystem fills the case of the airspeed indicator, providing a"base" pressure against an expandable diaphragm. Air forced into the pitot tube as theairplane moves fills the diaphragm, which expands as ram air pressure (and speed) increase. A needle connected to the diaphragm rotates as the diaphragm expands. The needle's position on the instrument face indicates airspeed

what is the difference between hydralic and pneumatic system

Pneumatic system is operated by compressed air while hydraulic system is operated with pressurised hydraulic oil
or any type viscous oil.
Hydraulic systems can usually produce higher control forces and work under extreme
operating conditions. This is the system that is primarily used on aircraft to move
control surfaces and engine controls.
You can often classify pneumatic systems because they have a pump (gas pump) and
hydraulic systems have a piston.
That is the difference. Also, pneumatic systems are louder because it is a gas under pressure.

1. By definition, hydraulics is used in controlling or harnessing power
with the use of pressurized fluids whereas pneumatics studies how pressurized
gases influences mechanical motion or movement.
2. Hydraulics uses an incompressible fluid medium like oil whereas pneumatics
uses a compressible gas like air.
3. Hydraulic applications demand greater pressures during operations that reach
thousands of pounds per square inch whereas pneumatic applications only
require 100 psi pressures more or less.
4. Most hydraulic applications generally use bigger components that pneumatic applications.
5. Hydraulic systems are generally more difficult to operate compared to pneumatic applications