নিম্নলিখিতগুলির মধ্যে কোনটি ঘর্ষণের একটি ভুল উদাহরণ?

Friction acts when surfaces slide against each other: a washing machine pushed on a floor, a sled on snow and a person on a slide all involve it. Lifting a heavy object straight up is working against gravity, not friction, so it is the wrong example.