SME
Grade 11 Science · Problem type
Is the net force zero?
Use this for “A cork floats still on water. What force balances its weight?” and other questions about balanced forces.
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Is the net force on it zero?
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Assumptions
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Zero net force means constant velocity, not zero speed: a steady speed in a straight line counts.
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Any change in speed or direction needs a net force, even at a steady speed round a curve.
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A floating cork is still, so the water’s upward push (the buoyant force) equals its weight.
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Related lessons
Forces and Newton's laws: friction, inclines and tension
Main lesson
A block sliding down an incline
Use this for “A 5 kg block slides down a 30° ramp with μₖ = 0.2. What is its acceleration?”
Pulling by a rope at an angle
Use this for “A 10 kg sled is pulled with 50 N by a rope 30° above level; μₖ = 0.1. Find the normal force and the acceleration.”
Hanging in an elevator
Use this for “A 3 kg lamp hangs from the ceiling of an elevator speeding up at 2 m/s² going up. What is the tension in its cord?”
Adding two forces
Use this for “Two dogs pull a 25 kg sled: 60 N east and 80 N north. What is the net force, which way, and the acceleration?”