A.2 · 1 · A.2 Forces and momentum · Newton’s laws
Newton's first law
The law of inertia: no net force, no change in motion.
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A puck glides across smooth ice and hardly slows down. What is pushing it along?
Newton’s first law
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A trolley moves at constant velocity on a level track. The net external force on it is…
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Which property of an object resists a change in its motion?
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A bus stops suddenly and passengers lurch forward. The best explanation is…
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A puck on frictionless ice is pushed and then released. Describe its motion after release and explain it with Newton’s first law.
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From lesson A.1 · 1
Motion is described…
From lesson 0.5
The unit newton in base units is…
Summary card
Key points
- • No net external force means no change in velocity.
- • Inertia is the property that resists a change in motion.
- • A moving object does not need a force to keep moving.
Formulas
- If Fnet,ext = 0 then Δv = 0 and a = 0
Key terms
- Inertia :
- the property that resists a change in motion
- Net external force :
- the total force from outside the object
Common errors
- • Thinking constant motion needs a constant force.
- • Forgetting that direction counts as part of velocity.
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