Answer: because she is pedalling at her maximum speed produced by the maximum force applied. At constant speed, acceleration is equal to zero.
Explanation:
Pedalling of bicycle involves application of force. The force applied produces circular motion to the tires which eventually transform into linear speed.
V = wr
Where V = linear speed
W = angular speed
r = radius.
Change in speed V will lead to acceleration or deceleration depending on increase or decrease in speed.
If she stops accelerating, then, she must have applied force that makes her pedalling at maximum speed. She is also maintaining this uniform (constant ) speed. After reaching her maximum speed.
At constant speed, acceleration = 0
Base on this explanation, even though she is still pedalling as fast as she can, which at constant speed, she will stop accelerating and her speed reaches a maximum value because she is pedalling at her applied maximum force.
