4-4 Magnitude of forces (5.2)

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

The magnitude of forces (p. 164)

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Lessonup

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                 Kilogram and newton

- Kilogram is the amount of matter

- Fore is measured in newton, the symbol for newton is N

On earth a force of 9,8 N is required to lift one kilogram of substance.

Force to pick something up

1 kg - force needed is 9,8 N

10 kg - force needed is 98 N

F = force in newton

m = mass in kilogram

g = gavitational acceleration in m/s²

F=m⋅g

Strongest muscles

• Muscles consist of muschle tissue
  
• By training your muscles the 
  

        your muscles grow and strengthen

• The strongest muscles are at the 
  

        front of yout thighs.

• They can deliver a force of 
  

        1 000 N.

Actvity 5 (p 170)

During the next lesson (1 test)

- You are going to hang masses on a 

    spring.

- you will measure the 

     extention of the spring

After that you will make a graph with the extention (in cm) plotted against the force.

              Measuring forces

- A spring balance is made up of a spring mounted in a cylinder.

- On the cylinder there is a scale division.

Symbols of forces

Which unit is used to measure mass?

1. kg
2. N
3. m
4. m/s

Which unit is used to measure force?

1. kg
2. N
3. m
4. m/s

The object with the largest mass experiences the greatest gravitational force.

1. true
2. false

What is the gravitational force on a watermelon that has a mass of 2 300 gram?

1. 22 540N
2. 23 N
3. 235 N
4. 0,2 N

What is the mass of a horse if the gravitational force on the horse is
7 350 N?

1. 72 030 kg
2. 750 kg
3. 700 kg
4. 1 000 kg

What is the symbol for frictional force?

1. Fw,l
2. Fz
3. Ff
4. Fv

The following questions are bout the practical investigation you will do the next lesson. Take 5 minutes to read (p 170)

What is placed on the vertical axis?

1. Mass
2. Gravitational force
3. Length of spring
4. Extension of spring

What is placed on the horizontal axis?

1. Mass
2. Gravitational force
3. Length of spring
4. Extension of spring

Now do 24 up to 28 

(p 165)

No discussion

10 minutes

when you are done -  read p. 166 and 167

What have
you learned?

Conclution:

• Mass we measure in kilograms (kg)
• Force is measured with
• The symbols for different forces are

F=m⋅a