Question

Alida runs her toy car on dry marble floor, wet marble floor, newspaper and towel spread on the floor. The force of friction acting on the car on different surfaces in increasing order will be

• A. wet marble floor, dry marble floor, newspaper and towel.
• B. newspaper, towel, dry marble floor, wet marble floor.
• C. towel, newspaper, dry marble floor, wet marble floor.
• D. wet marble floor, dry marble floor, towel, newspaper

Answer 1

The correct option is A

wet marble floor, dry marble floor, newspaper and towel.

1. Friction is the force that is generated by the contact of two rough surfaces and opposes the motion.
2. Clearly, frictional force acting on a body on a rough surface is greater compared to the friction acting on an object in a less rough place.
3. If the place is wet then there will be a decrease in the contact of rough surfaces which results in a decrease in the friction force.
4. So frictional force is directly proportional to the roughness of the surface.
5. The given surfaces are dry marble floor, wet marble floor, newspaper, and towel spread on the floor.
6. The towel has the roughest surface among all other given objects.
7. The newspaper is rougher than a dry marble floor surface, so it will have a place before the towel.
8. We know that friction on a wet surface is less than friction on a dry surface.
9. So friction forces will be lesser on wet surfaces rather than on dry surfaces, so wet marble floor will win here.
10. So the correct order is Wet marble floor $<$Dry marble floor $<$ Newspaper $<$ Towel.

Hence, option A is correct.