Question

which of the following is the best example of friction?
a) a vase of flowers sitting on a table.
b) a bike tire being squeezed by a brake.
c) an apple falling to the ground from a tree.
d) a bowling ball rolling down the lane at a constant speed.

Explanation:

Friction is a force that opposes motion between two surfaces in contact.

• Option A: A vase sitting on a table has no relative motion between surfaces (vase - table), so no significant friction related to motion.
• Option B: When a bike tire is squeezed by a brake, the brake pad and the tire surface rub against each other. This rubbing (contact of two surfaces with relative motion) creates friction which slows down the bike.
• Option C: An apple falling is due to gravity, not friction.
• Option D: A bowling ball rolling at a constant speed. If there was significant friction (like kinetic friction opposing motion), the ball would slow down. Since it's at constant speed (assuming no external force to counter friction, which is not the case here as per the problem - we are just looking for the best example of friction), the main force here is not friction in the context of opposing motion as strongly as in the brake - tire case.

Answer:

B. A bike tire being squeezed by a brake.