4-7 magnitude of forces (4.2 knowing more)

• Natuurkunde
• Middelbare school
• havo, vwo
• Leerjaar 2

The magnitude of

a force (p 169)

Bluetooth 

- ON

Lessonup

- YES

Stationary

- Books

- Pen and calculator

Mark

- No

Lesson goals:

• What does 'elastic' mean
• What does 'stiff' mean
• Make calculations if the  

       tensile strength of a material 
       is known

Streaching and bending

Everything can stretch.

A rubber band is elastic, 

because it returns to its 

original length.

But even steel wire and a thick 

steel cable streaches a little bit.

Stiff

• Steel is stiffer than rubber. 
  
• Therefore you need a greater 

       pulling force to stretch steel. 

• Thickness and shape also influence the size of the required pulling force. 
  
• Huge buildings move a bit in the wind.

Bend or break

A weak material can break 

due to tensile or bending forces. 

E.g. a bridge breaks if the traffic 

that crosses it is too heavy.

                     Tensile strength

                                          The tensile strength of steel is 400 N/mm²

This means that a steel cable with a cross-sectional area of 

 1 mm² breaks under a load of 400 N.

Paper has a tensile strength of approximatly 100 N/mm².

^{Designers have to take these strengths into consideration.}

Make 37 up to 40 

(p 169)

no discussion

Answers will be typed into your iPad

When you are done, read mroe about 'largest engineering disasters'

37a

1. handle
2. strings
3. frame

37b

1. handle
2. stings
3. frame

38a

1. bowstring
2. bow

39a

1. 27
2. 9
3. 81
4. 3

40a

1. 3N
2. 30N
3. 29,4N
4. 3kg

40b

1. 29,4
2. 294
3. 2,94
4. 0,29

40c

1. 1176
2. 136
3. 0,0074
4. 2,94

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learn today?