helpful friction would be the friction on something that you wanted to stop (a car) while unhelpful friction is friction on something that you want to keep going (a curling rock)
Friction is a force that can be both helpful and unhelpful. Examples of helpful frictions include walking and driving, while unhelpful frictions can occur in engines and when moving heavy objects. Understanding how friction works can help us utilize it effectively while minimizing its drawbacks.
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