lesson
Resistance depends on the situation
1 · Learn
Water resistance can oppose an object's motion through water. Friction can oppose relative motion where surfaces contact each other. Streamlined shapes can reduce fluid resistance in suitable conditions.
Resistance is not always unwanted. Friction helps shoes grip the ground and brakes slow a wheel. Explain the job before deciding whether more or less resistance is helpful.
2 · Worked example
I compare a swimmer's streamlined position with a broad shape moving through water, while remembering speed and other conditions affect the force too.
3 · Your turn
Give one situation where friction is useful. Does that mean the greatest possible friction is always best?
Check your answer
Grip between shoes and ground or braking can be useful. No: the useful amount depends on the task and conditions.
4 · Apply your learning
Use safe adult-provided observations to compare movement over surfaces or through water. Identify the force and relevant controlled conditions.
Adult guidance and safety
No swimming experiments, slippery floors or unsafe braking tests. Keep small cold-water models away from electricity.
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