Forces

• Natuurkunde
• Middelbare school
• vwo
• Leerjaar 3

Forces

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Using levers

Learning goals

1. You know that Force is the quantity and Newton it's unit. 
2. You can calculate the magnitude of gravity by using Fg= m × g.
3. You know why we use a lever and you can explain how it works. 
4. You can explain what the arm of the force is. 
5. You can explain that an object is stable when its centre of gravity is above the support surface.

Forces

Force (F) is the quantity, we measure forces in the unit Newtons (N)

You can't see forces, only its results.  For example:

• The objects changes speed
• The object changes direction
• The objects deforms

Gravitational force

A form of force is gravity, we can calculate the magnitude of the gravity with the formula:

Fg = m × g

Fg= the gravity in Newtons

m= the mass in kilograms

g = 9.81 N/kg on earth

Gravity works from the centre of gravity

Using levers

We use levers to increase the working force. For example a bottle opener. 

The tools have a:

• fulcrum or pivot point
• a short end where the working force acts
• a long end where the muscular force acts

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Calculations with levers

Learning goals

1. Explain the function of a counter weight
2. Check when a lever is in equilibrium / balance
3. Do calculations using the law of the lever: F1 × r1 = F2 × r2

Ratio of working force and muscular force

To maximise the working force, you need to make sure the arm of your muscular force is as large as possible.

Small arm, big force
Big arm, small force

Equilibrium

Counterweights

Draw bridges use a counterweight.