Engineering Unit: Grade 9 science IB

Question 1

What is a Mechanical Property?

Answer 1

A mechanical property determines how a material will react when it is subjected to one or more mechanical constraints.

Question 2

List the types of Mechanical Properties:

Answer 2

1. Hardness (resists penetration)
2. Elasticity (returns to original shape)
3. Resilience (resists physical impacts)
4. Ductility (stretches without breaking)
5. Malleability (flattens or bends without breaking)
6. Tensile strength (resists tension, elastic)

Question 3

What is a mechanical constraint?

Answer 3

A mechanical constraint describes the stress produced within a material when it is subjected to one or more external forces; mechanical constraints produce various effects inside a material.

Question 4

List the 5 principle mechanical constraints:

Answer 4

1. Compression (crushes materials)
2. Tension (force that stretches materials)
3. Torsion (force that twists materials)
4. Bending (force that bends materials)
5. Shearing (force that cuts/tears materials)

Question 5

What are the 4 mechanical functions?

Answer 5

• Link
• Guide
• Lubrication
• Seal

Question 6

Define a link:

Answer 6

Links are used to connect 2 or more parts of an object.

Question 7

Define a guide:

Answer 7

Forces a part to follow a certain guiding motion (translation/rotation)

Question 8

Definition of lubrication:

Answer 8

Reduces friction by technical means.

Question 9

Definition of seal:

Answer 9

Prevents a gas or liquid from escaping.

Question 10

Types of guiding:

Answer 10

Rotations, Translation, Helical

Question 11

Gear Train:

Answer 11

• Components of a gear train include and driver, and a follower, sometimes they also include intermediates.
• In a gear train each gear turns opposite in direction to the gear(s) directly beside it
• Reversible
• Motion Transmission system: rotation - rotation
• Should be lubricated

Question 12

Chain and Sprocket systems:

Answer 12

• Components of a chain and sprocket system include gears, and a chain .
• In a chain and sprocket system gears within the train turn one way, and gears outsides the chain turn the opposite direction.
• Reversible
• Motion Transmission system: rotation - rotation
• Should be lubricated

Question 12

Chain and Sprocket systems:

Answer 12

• Components of a chain and sprocket system include gears, and a chain .
• In a chain and sprocket system gears within the train turn one way, and gears outsides the chain turn the opposite direction.
• Reversible
• Motion Transmission system: rotation - rotation
• Should be lubricated

Question 13

Friction gear system

Answer 13

• Components of a friction gear system include and driver, and a follower, sometimes they also include intermediates.
• In a friction gear system each gear turns opposite in direction to the gear(s) directly beside it
• Reversible
• Motion Transmission system: rotation - rotation
• Should NOT be lubricated
• Diameter = teeth (equivalent to gear train)

Question 14

Belt and Pulley system

Answer 14

• Components of a belt and pulley system include pulleys (gears without teeth), and a belt.
• In a belt and pulley system pulleys within the belt turn one way, and pulleys outsides the belt turn the opposite direction.
• Reversible
• Motion Transmission a system: rotation - rotation
• Should NOT be lubricated

Question 15

Wheel and worm-wheel system

Answer 15

• Components of a wheel and worm-wheel system include a worm-wheel (screw), whose rotation is transmitted to one or more wheels.
• In a wheel and worm-wheel system both the wheel and worm-wheel both rotate in the same direction.
• NOT reversible, the worm-wheel is ALWAYS the driver
• Motion Transmission system: rotation - rotation
• Should be lubricated

Question 16

Rack and Pinion system

Answer 16

• Contains at least one gear called a pinion, and a straight, teethed bar called a rack,
• Reversible
• Motion Transformation System : Rotation - translation (& vice versa)
• Should be lubricated

Question 17

Screw-Gear System

Answer 17

• Contains a screw and a nut
• Irreversible; nut rotates and transforms into the translational motion in the screw. The nut it always the driver
• Motion Transformation System : Rotation - translation
• Should be lubricated

Question 18

Cam and follower system

Answer 18

• Contains a cam (egg shaped piece), and a follower (a stick that bobs).
• NOT Reversible, Cam is ALWAYS driver
  *Follower follows…lol…. It is driven.
• Cam rotates, Follower translates
• Motion Transformation System : Rotation - translation
• Should NOT be lubricated

Question 19

Slider-crank mechanism

Answer 19

• Contains a crank, slider, and guide.
• Reversible, crank and slider can switch which is driver/driven
• Crank rotates like wheels, slider translates like a piston
• Motion Transformation System : Rotation - translation (& vice versa)
• Should be lubricated

Question 20

Speed Change!

Answer 20

Increase: Driver is bigger/has more teeth than driven
Decrease: Driven is smaller/has less teeth than driven
No Change: Driver and driven are the same in size/teeth

Question 21

Define exploded view

Answer 21

Shows all components of an object separated from each other.