The foot of a 55 kg sprinter is on the ground for 0.25 s while her body accelerates from rest to 2.0 m/s. (b) What is the magnitude of the friction force?

Key Concepts

Newton's Second Law of Motion

Newton's Second Law states that the acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass. This relationship is expressed by the formula F = ma, where F is the net force, m is the mass, and a is the acceleration. Understanding this law is crucial for calculating the friction force acting on the sprinter as she accelerates.

Friction Force

Friction force is the resistance that one surface or object encounters when moving over another. It is influenced by the nature of the surfaces in contact and the normal force acting between them. In this scenario, the friction force is what allows the sprinter to accelerate from rest, and it can be calculated using the coefficient of friction and the normal force.

Kinematics and Acceleration

Kinematics is the branch of mechanics that deals with the motion of objects without considering the forces that cause the motion. In this problem, we need to determine the acceleration of the sprinter, which can be calculated using the change in velocity over time. The sprinter accelerates from 0 to 2.0 m/s in 0.25 seconds, allowing us to find the acceleration needed to apply Newton's Second Law.