MomentsEdexcel GCSE Physics: Flashcards

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Define a moment.

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Define a moment.: The turning effect of a force about a pivot.
State the equation for calculating a moment.: moment (N m) = force (N) × distance normal to the direction of the force (m).
What units are moments measured in?: Newton-metres (N m).
What distance must be used when calculating a moment?: The distance measured perpendicular (at right angles) to the line of action of the force, from the pivot.
State the principle of moments.: For an object in equilibrium, the sum of the clockwise moments about a pivot equals the sum of the anticlockwise moments.
Calculate the moment produced by a 15 N force acting 0.4 m from a pivot.: moment = 15 × 0.4 = 6 N m.
How does a lever make a task easier?: It lets a small effort force applied far from the pivot produce a large moment, which can move a heavy load positioned close to the pivot.
What do gears transmit between connected wheels?: Rotational (turning) forces and motion.
What happens to turning force and speed when a small gear drives a larger gear?: The turning force (moment) transmitted increases, but the larger gear turns more slowly.
Give an everyday example of a lever.: A crowbar, a pair of scissors, or a see-saw.
If an object is in rotational equilibrium, what does this tell you about the resultant moment?: The resultant moment on the object is zero — it is not rotating (or turning at a constant rate).