Mechanical systems and control

Question 1

What is a mechanism?

Answer 1

A mechanism is a set of moving parts used to make work easier.

Question 2

What is a lever?

Answer 2

A simple mechanism used to move weights by a bar that turns around a fixed point. Levers make moving, prying, lifting and shifting objects much easier.

Question 3

What is a fulcrum?

Answer 3

The pivot on which the arm of a lever moves

Question 4

How do levers work?

Answer 4

All levers have a rigid, straight arm that turns around a fixed point, called the fulcrum. The fulcrum can be anywhere along the arm.

Question 5

What is the effort?

Answer 5

The force exerted in a mechanism that enables it to work e.g. a hand pulling a bottle top opener.

Question 6

What is the load?

Answer 6

The weight/mass that needs to be lifted, cut or moved.

Question 7

Name the three types of levers and the differences between them.

Answer 7

First class levers - fulcrum in the middle - effort is in the opposite direction to the load. (FEL)
Second class levers - load is in the middle - effort is in the same direction as the load (FLE or ELF)
Third class levers - effort is in the middle - effort is in the same direction as the load. (LEF)

Question 8

What is mechanical advantage?

Answer 8

When a mechanisms allows us to move a large load with a small effort. It is determined by the length of the bar, the position of the fulcrum and the position of the force and the load.

Question 9

What are load and effort measured in?

Answer 9

Newtons

Question 10

Is there mechanical advantage in first class levers?

Answer 10

It depends on where the fulcrum is positioned. If the fulcrum is positioned close to the load and the distance between the fulcrum and the effort is bigger, there is Mechanical advantage. If the fulcrum is in the centre between the load and the effort and the two are balanced there is no mechanical advantage.

Question 11

How do you calculate mechanical advantage?

Answer 11

MA = load/force. The greater the MA, the more the lever helps you.

Question 12

Is there mechanical advantage in second class levers?

Answer 12

Yes but requires increased effort.

Question 13

What will improve the mechanical advantage of a second class lever i.e. moving a large load with small effort?

Answer 13

If the load is very close to the fulcrum

Question 14

Give me an example of a first, second and third class lever.

Answer 14

First class lever: See Saw
Second class lever : Wheelbarrow
Third class lever: Human arm

Question 15

IS there mechanical advantage in third class levers?

Answer 15

No. The effort must always be greater than the load.

Question 16

What are the advantages of third class levers?

Answer 16

They can move a load a long distance relative to effort.

They are easy to use.

Question 17

What are linkage systems?

Answer 17

Two or more levers that are joined together

Question 18

What are two joined levers called?

Answer 18

Paired levers

Question 19

Where is the fulcrum usually positioned with paired levers?

Answer 19

The fulcrum is where the two levers join.

Question 20

What is the advantage of linked third class levers?

Answer 20

They allow us to make precise and accurate movements.

Question 21

What is a complex linkage?

Answer 21

It is made up of a number of levers joined together e.g. a security gate.

Question 22

What are linkages used for?

Answer 22

Change the direction of a movement
Change the distance of a movement
Allow parts to move in parallel with one another
Allow two or more items to move at the same time.

Question 23

What is a pneumatic system?

Answer 23

A mechanical system that uses compressed air to give us mechanical advantage for tasks.

Question 24

Define a force

Answer 24

An effort that can move an object usually a push or a pull.

Question 25

Pneumatic systems are open systems. What does this mean?

Answer 25

An open system lets something like air in or out.

Question 26

What is a hydraulic system?

Answer 26

A mechanical system that uses liquids under pressure to give us mechanical advantage.

Question 27

Hydraulic systems are closed systems. What does this mean?

Answer 27

A closed system contains a fixed amount of the substance e.g. liquid under pressure and does not allow any of the substance in or out.

Question 28

Do hydraulic systems provide high or low mechanical advantage?

Answer 28

Very high mechanical advantage because liquid cannot be compressed so pressure on the liquid produces an immediate output response.

Question 29

Give me an example of a pneumatic system.

Answer 29

Bicycle pump, dentist drill

Question 30

Give me an example of a hydraulic system.

Answer 30

Car braking systems