Biomechanics- Linear motion Flashcards

Question

Answer 1

* Air resistance (1) this will be acting in the opposite direction of travel to the jumper / will depend on the velocity of the jumper / the cross sectional area of the jumper / the streamlining / shape of the jumper (1) * Weight / Gravity (1) this will be pulling the jumper downwards towards the sand pit / the greater the mass of the jumper the greater the weight force will be pulling the jumper down (1). Accept other appropriate explanations of the external forces acting on the athlete.

Answer 2

A. (start of the race) Graph C – large positive impulse indicating acceleration. B. (middle of the race) Graph A – positive and negative impulse equal showing constant speed. C. (end of the race) Graph B – large negative impulse indicting deceleration. D. If all three graphs in correct order (C, A, B) but explanation incorrect.

Answer 3

Award one mark for each of the following points: * A measure of force applied over time / Impulse = force x time (1) * Measured in Newton seconds / Ns (1) Do not accept newtons per second / NS-1 / N/S Accept any other appropriate definition of impulse. Answers must refer to force and time. (b) [AO2 = 3] Award one mark for each of the following points: * X axis: time s / seconds, Y axis: force N / Newtons (1) * Negative and positive components of force shown with negative first (1) * Positive impulse larger than negative impulse (1)

Answer 4

**AO1 − Knowledge of impulses** E.g. an impulse is the change of momentum of an object when the object is acted upon by a force for an interval of time. It is caused by a force during a specific time interval. Impulse = force × time and is sometimes referred to as force vs time graphs. * X axis − (time)/milliseconds/seconds * Y axis − (force)/Newton’s * shape of impulse graphs − negative and positive components of force shown with negative first. **AO2 general points** General points: * axes should be appropriately labelled * differentiation between negative and positive impulse should be obvious * mass of the runner would remain constant * net impulse is combination of negative and positive impulses. Leaving the blocks: * net impulse is positive * the performer is accelerating. Between 40–80 m: * positive and negative impulses relatively equal * net impulse of zero / negligible. After crossing the line: * net impulse is negative * deceleration. ** AO3 − Justification of answers** E.g. leaving the blocks − The positive aspect of the graph is bigger than the negative. When leaving the blocks the runner would hope to gain a positive impulse to accelerate. The greatest proportion of the graph is above the line and therefore shows the positive force in Newton’s law. The take-off / drive toe / ball of foot would create force for a relatively short amount of time as quick feet movement would be key to gain the acceleration. The breaking impulse (negative) is less than propulsive impulse (positive) / movement / contact with ground to limit breaking impulse. There must be appropriate ground reaction force to generate acceleration. Between 40–80 m − There is a relatively stable nature of the middle of the race necessitates a relatively equal impulse. The proportions of the graph are fairly equal and there is a balancing of breaking impulse (negative) with propulsive impulse (positive) to maintain speed being generated. The importance of the middle section is to maintain position or to ensure speed is maintained to match or better opposition. There is no acceleration / deceleration / running at constant velocity / speed. After the finish line − The negative aspect of the graph is bigger than the positive. After crossing the line, the runner would hope to gain a negative impulse to decelerate. The greatest proportion of the graph is below the line and therefore shows the negative force in Newton’s law. The landing foot is accentuated onto the ground for a longer time than during the race. The breaking impulse (negative) is more than the propulsive impulse (positive) / movement / contact with ground to increase breaking impulse. The importance of appropriate ground reaction force is to generate deceleration. Accept any other relevant justification of the impulses that would be produced at the various stages of the 100m race.

Answer 5

X Axis – (time) / milliseconds / seconds Y Axis – (force) / Newton’s Axis must be labelled with correct units to be credited. Accept with just units Shape of graph – negative and positive components of force shown with negative firstPositive impulse clearly larger than negative impulsePositive and negative (force) labelled Only awarded if negative impulse is first in the diagram