Multiple choice

How can we increase the force of friction?

  1. By polishing

  2. By greasing

  3. By oiling

  4. By throwing sand on tracks covered with snow
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Throwing sand on snow-covered tracks increases surface roughness, which increases friction between wheels/feet and the track. This provides better traction on otherwise slippery surfaces. The other options (polishing, greasing, oiling) all decrease friction.

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