The Figure shows a velocity/time graph for an elite 100-metre runner.
(i) Use the figure to determine the velocity of the sprinter after 3 seconds, and identify the period of time when the sprinter’s acceleration was the greatest. (2 marks) (ii) What is happening to the sprinter between 6 and 11 seconds? Explain why this occurs. (3 marks)
The performer cannot move the earth but receives significant acceleration
This is called Ground Reaction Force
Action force of muscle contraction Equal and opposite force
Using Newton’s Laws explain how an athlete accelerates out of the blocks at the start of a race.
The athlete remains at constant velocity, at rest, in his blocks at the start of a race due to Newton’s First Law – the Law of Inertia. In order for him to accelerate an external force must be applied.
As the athlete uses his muscles to generate a force into the blocks/ground there will be an equal an opposite reaction force pushing him forwards, due to Newton’s Third Law – the Action-Reaction Law.
This resultant force is the external force required to overcome the inertia (Newton’s 1st Law) and the athlete accelerates from the blocks.
The acceleration of the athlete is in direct proportion to the size of the resultant external force due to Newton’s Second Law – the Law of Acceleration. The acceleration can be calculated using the formula F=ma.