Bumblebee

problem: two trains enter a tunnel 200 miles long (yeah, its a big tunnel) travelling at 100 mph at the same time from opposite directions. as soon as they enter the tunnel a supersonic bee flying at 1000 mph starts from one train and heads toward the other one. as soon as it reaches the other one it turns around and heads back toward the first, going back and forth between the trains until the trains collide in a fiery explosion in the middle of the tunnel (the bee survives). how far did the bee travel?

Solution

solution: this puzzle falls pretty high on my aha scale. my first inclination when i heard it was to think “ok, so i just need to sum up the distances that the bee travels…” but then you quickly realize that its a difficult (not impossible) summation which the interviewer could hardly expect you to answer (unless i guess if you are looking for a job as a quant). “there must be a trick” you say. eh, sort of i guess, enough to say that this question is a stupid interview question.

the tunnel is 200 miles long. the trains meet in the middle travelling at 100 mph, so it takes them an hour to reach the middle. the bee is travelling 1000 mph for an hour (since its flying the whole time the trains are racing toward one another) – so basically the bee goes 1000 miles.

there is no process to explain, so this question can’t possibly teach you anything about the person. they either know it or they don’t and if they already knew it before you asked, you’re not going to be able to tell when they give you the answer. so don’t ask this question. and if someone asks you this question, just tell them you’ve already heard it before.

JIB CRANE

Jib crane have the following motions:

1. Hoisting motion
2. Derricking or luffing motion
3. Slewing motion
4. Long travel motion

Hoisting motion:

It is used to lift or lower the load. This is usually achieved by steel wire ropes being affixed to a crane hook or a grab hanging from the outer end of the jib. The rope is applied through some receiving arrangement and controlled and operated by a winch system.

Derricking or Luffing motion:

It is imparted to the inclined member or the jib to move in a vertical plane so that the angle of the jib may be changed in order to bring the load line nearer to or further off from the centre of the crane.

Slewing motion:

It is imparted to the whole super structure of the crane including the jib, so that it can turn about a central pivot shaft w.r.t. the non-revolving parts. This motion enables the crane to shift the load line to revolve round the crane.

Long Travel Motion:

It may be required when the whole crane structure has to be shifted to a distant place along a rail track or along a road.

Jib crane consists of an inclined member supported by a rope or any other type of structural member attached to a vertical mast or frame. Load is usually suspended from the outer end of this inclined mast. The outreach of the jib may be fixed or variable. The cranes as a whole may be either fixed or moveable. Various sub-classification of these cranes are possible.

Lifting capacity of such cranes may vary from 1/2 ton to 200 ton and outreach from a few meter to 50 meter. Such cranes find various applications in port area, construction site, and other outdoor works.

For handling general cargo, lifting capacities are usually 1  1/2 ton to  5 ton with maximum outreach of 30 meter. Jib Cranes provided with grabbing facilities have usually a capacity ranging from 3 to 20 tons operating 50 to 100 cycles per hour. Lifting heights may be 30 meters or more.

Jib crane used in ship yards for lifting heavy machinery and equipment, weighing 100 to 300 tons, are usually mounted on pontoons. Frequently these cranes are provided with two main hoisting winches which can be employed singly or together to lift a load. For handling light loads these cranes may have auxiliary arrangement.

Types Of Jib Crane:

Depending on the use, jib cranes are classified into a number of varieties, primarily on the basis of their mountings.

These are:

1. Hand Operated Scotch Derrick Type
2. Wall Mounted Jib crane
3. Portal / Semi-portal cranes of different varieties-Wharf cranes
4. Mobile jib cranes consisting of truck mounted and crawler mounted cranes

Scotch Derrick Type / Wall Cranes:

Wall cranes are used in ware houses for handling light weight and when there is little or no wharf between them and the water front. Slewing or rotational motion of the crane is possible within restricted angle and the motion is slow. Hoisting and lifting speeds are comparable to those of wharf cranes. In some modified version these cranes can have travelling speed along the wall.

Wharf Cranes:

These are used in shipyard and port for handling unit and bulk load. These are usually self propelled balanced level luffing type with full circle slewing motion facility. Wharf cranes may be of different types, depending on the type of structure on which it is mounted.  The choice of structure for mounting depends on site condition.

The principal types of wharf cranes are:

• High pedestal
• Full Portal
• Semi-portal

Portal Cranes:

Portal crane is a fixed or revolving type jib crane mounted on a portal frame fixed in location or arranged to travel along a fixed track of rails at the same level. The portal frame consists essentially of horizontal girders connected at both ends to vertical or inclined member’s having equal lengths.

Semi portal Crane:

Semi portal crane is a fixed or revolving type jib crane mounted on a semi portal frame fixed in location or arranged to travel along a fixed track or rails at different levels. The semi portal frame essentially consists of horizontal girders connected at both ends to vertical or inclined members which constitute a shorter side and a longer side. The shorter members may consist only of the trolley running along the elevated rail.

Mobile crane:

Mobile Crane ( Power Driven ) includes all type of travelling jib cranes, such as truck mounted, crawler mounted, locomotive crane on rails.

 

CONVEYOR LAYOUT

Conveyor layouts:

Belt conveyors can be designed for practically any desired path of travel. It should be noted that transfer between conveyors should be avoided where possible due to additional wear on the belts at the loading points. Some of the profiles shown below:

Horizontal Conveyor

 

 

Decline Conveyor

Inclined Conveyor

Overland Conveyor

CONVEYOR LAYOUT

Conveyor layouts:

Belt conveyors can be designed for practically any desired path of travel. It should be noted that transfer between conveyors should be avoided where possible due to additional wear on the belts at the loading points. Some of the profiles shown below:

Horizontal Conveyor

 

 

Decline Conveyor

Inclined Conveyor

Overland Conveyor