Vertical Impulse Research Paper

Question 1(a)

Explain what is impulse. Describe how you obtain the total vertical impulse through the use of a force platform. (20 m)

When performing a squat jump, the force produced by the subject is applied over a period of time. The overall effect of this force acting over time is known as impulse. Impulse can be derived by mutiplying the force with time. It is measured in Newton-second (N-s). The vertical impulse is therefore the product of the vertical ground reaction force and time. In a force-time graph of a squat jump, it can be defined as the area under the curve. The priciple of impulse-momentum relationship states that the change in momentum of an object is in proportion to the net impulse applied. Momentum is the quatity of motion

Force-time graph of a squat jump. Question 1(b)

Demonstrate your competence in kinetic analysis by the obtaining and presenting vertical jump impulse using the force-time data obtained from force platform. (20 m)

In figure 1, the propulsive phase is indicated by the green and red lines. The green line indicates the start of the jump whereby the subject is beginning to to exert force and the red line indicates the time just before the take-off. From Table 1, the total vertical impulse which includes the body mass impulse is 320.5 N-s, during this phase. The time taken is 0.471 seconds. Table 1. Vertical ground reaction force data – Total vertical impulse To calculate the vertical jump impulse, find the difference between the total vertical impulse and the body mass impulse. The body mass impulse can obtained from the graph. The body mass impulse is 234.2 N-s for the similar period of time of 0.471 seconds. (Table 2) igure 1. Force-time graph of a squat jump (Body Mass) http://dc.etsu.edu/cgi/viewcontent.cgi?article=2652&context=etd impulse on vertical jumps https://www.youtube.com/watch?v=cQFecjeJNso Figure 2. Force-time graph of a squat jump – Body mass impulse Table2. Vertical ground reaction force data – Body mass

Question 1(c)

Illustrate how you can calculate the final vertical velocity of the jump from the jump impulse. (40 m)

From the impulse-momentum relationship, one can derive that the change in the velocity of the jump will directly affect the vertical jump impulse. The impulse-momentum theorem (ΣFt = mvf - mvi ) is used to find the final vertical velocity of the jump. ΣFt is the net vertical jump impulse, m is the mass of the object, vf is the final velocity and vi is the initial velocity. The net vertical jump impulse (ΣFt) of 86.3 N-s is obtained by finding the difference between the total vertical impulse and the body mass impulse. From a squat jump, the initial velocity of the jump is zero, so the product of body mass and initial velocity will be zero (mvi = mass x 0m/s = 0). Thus, to find the final vertical velocity of the jump, the net vertical jump impulse is divided by the body mass, so ΣFt / m = vf. The subject’s body mass is 58 kg. Therefore,

Final vertical velocity at take-off = = 1.48 m/s

Hence, the final vertical velocity of the subject at take-off is 1.48