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Cause and Effect — Forces at Work
Forces and What They Do
Two objects interact (a push or a pull)
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Contact forces
Muscular force and friction act through touch
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Non-contact forces
Magnetic, electrostatic and gravitational act from a distance
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Objects start, stop, change motion or shape; weight, floating and sinking follow
Mind Map
Exploring Forces
Chapter 5
5.1
What is a force
A push or pull; unit newton (N)
5.2
Effects of force
Start, stop, change speed, direction, shape
5.3
Interaction
At least two objects interact for a force
5.4.1
Contact forces
Muscular force; friction opposes motion
5.4.2
Non-contact forces
Magnetic, electrostatic, gravitational
5.5
Weight
Earth's pull in N; mass vs weight; spring balance
5.6
Floating & sinking
Buoyant force vs gravity
Key Terms and Definitions
- Force
- A push or pull on an object from its interaction with another object.
- Newton (N)
- The SI unit of force and of weight.
- Contact force
- A force that acts only when objects are in physical contact.
- Muscular force
- The force produced by the action of muscles in the body.
- Friction
- The contact force that opposes one surface moving over another.
- Non-contact force
- A force felt even when objects are not in contact.
- Magnetic force
- The force a magnet exerts on another magnet or magnetic material.
- Static charge
- Electric charge built up on a rubbed object that does not move by itself.
- Charged object
- An object that has acquired static charges.
- Electrostatic force
- The force a charged body exerts on another charged or uncharged body.
- Gravitational force
- The Earth's pull on objects towards itself; always attractive.
- Vertical motion
- Motion in a vertical direction under gravity.
- Weight
- The force with which the Earth pulls an object; measured in newton.
- Mass
- The amount of matter in an object; the same everywhere.
- Spring balance
- A device that measures weight from the stretch of a spring.
- Buoyant force (upthrust)
- The upward force a liquid applies on an object in it.
- Archimedes' Principle
- An immersed object feels an upward force equal to the weight of liquid it displaces.
