Question

When a bicycle travels on a rough surface, its speed
A. Increases
B. Decreases
C. Remains the same
D. None of these

Answer 1

Hint: Before going to the question let us first know about friction. Friction is a force that prevents rigid objects from sliding or rolling over each other. Frictional forces, such as the traction needed to walk without falling, may be helpful, but they also provide significant resistance to motion.

Complete answer:
Friction is the force exerted by two surfaces sliding (or attempting to slide) over one another. When you try to drive a book across the concrete, for example, friction makes it difficult. Friction often acts in the opposite direction from where the object is going or attempting to move.

The forces of attraction, known as adhesion, between the contact regions of the surfaces, which are often microscopically irregular, tend to be the primary cause of friction between metals. Shearing these "welded" junctions, as well as the irregularities of the harder surface ploughing over the softer surface, cause friction.

The bicycle decelerates as it travels over the rough surface due to friction. The object's speed will be reduced before it has finished its journey over the rough surface. As the cycle progresses and reaches the smooth surface, the speed will naturally increase because the force of friction will be much lower.

So, the correct option is B.

Note: Work done against friction is path dependent since friction is a non-conservative force. Since some kinetic energy is often converted to thermal energy in the presence of friction, mechanical energy is not conserved.