Contact and Non-Contact ForcesAQA GCSE Physics: Flashcards

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What is a contact force?

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What is a contact force?: A force that only acts when two objects are physically touching.
Name four contact forces.: Friction, air resistance, tension, normal contact force.
What is a non-contact force?: A force that acts between objects that are physically separated.
Name the three non-contact forces in this specification.: Gravitational force, electrostatic force, magnetic force.
What is friction?: A contact force that opposes the relative motion of two touching surfaces.
What is tension?: The pulling force transmitted through a stretched rope, string or cable.
What is the normal contact force?: The support force a surface exerts at right angles to itself on an object resting on it.
What is the equation for weight?: W = mg, where m is mass in kg and g is gravitational field strength in N/kg.
Why is weight considered a non-contact force?: Because gravity acts on an object even when nothing is touching it.
Where does weight act on an object?: At the object's centre of mass.
How is weight measured?: Using a calibrated spring balance, also called a newtonmeter.
Is mass or weight the same on the Moon as on Earth?: Mass stays the same; weight is less on the Moon because gravitational field strength is lower there.
A 5 kg object is on Earth where g = 9.8 N/kg. What is its weight?: 49 N (W = mg = 5 × 9.8).
When two objects interact, what happens to the forces between them?: Each object exerts a force on the other — the forces act as a pair.
Is gravitational force a contact or non-contact force?: Non-contact — it acts between objects with mass even when they are not touching.