Answer to Question #80083 in Mechanics | Relativity for Poppy

Question

An articulated lorry has six pairs of wheels.
One pair of wheels can be raised off the ground.
Use your knowledge of physics, comment on situations in which the wheels may be raised or lowered.

Thank you

Answer 1

If agree that the centre of gravity is in geometrical centre of the lorry, between 3rd and 4th pairs of wheels, the wheels can be raised off the ground in the following situations.

To decrease the load on ball-bearings and tires and to increase its lifetime during no-load periods, much money will be saved. Raising up the wheels will also decrease the friction between the wheels and the ground ⇨ decrease fuel consumption. If the lorry has a load, the lowering wheels can be lowered to decrease the load on the suspension according to
pressure=(force of weight)/area.
Also rising the back pair of wheels distinctly decreases turning radius ⇨ increases maneuverability.

To drive over obstacles and high barriers: lower second or third pair of wheels (in motion direction) to let the first pair be over an obstacle, then raise these wheels up and go through.

To fix the lorry: lower the wheels to get to the space under the lorry.