Makeup Lab

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Temple University *

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3202

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Mechanical Engineering

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Dec 6, 2023

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KIN3202-Biomechanics of Physical Activity 1 Moment of Inertia Laboratory Introduction: The moment of Inertia is an objects resistance to rotation motion. In which m is mass of the object and k is the radius of gyration. The radius of gyration is the distance from the point of concentration of mass to the axis of rotation (A of R). The moment of inertia depends on an objects 1.) Mass and 2.) Where the mass is concentrated with respect to the A or R.  As the mass is concentrated further from the A of R  “I” is increased and therefore, the object is harder to rotate  As the mass is concentrated closer to the A of R  “I” is decreased, and therefore the object is easier to rotate. Materials: Golf clubs, foam golf balls, zepp sensor, and tape measure Activity 1: Directly measure the moment of inertia (I).  Take both the driver and an iron. Attempt to balance the shaft of the club on your finger like a pen or pencil. When you find the spot it balances, measure the distance from your finger to the end of the hand grip with the tape measurer in meters. Fill this in for “K” in table 1 below.  The weight of the driver is 2lbs and the weight of the iron is 2.5lbs. To convert these numbers to mass (kg) you will need to divide each by 2.2. Fill these numbers in for “m” in table 1.  Finally calculate I for both clubs by using the moment of inertia formula to complete table 1. Table 1 Club I (kg m 2 ) k (m) m (kg) Driver 0.2304 0.8 0.36 Iron 0.3881 0.95 0.43  Repeat the same process except now “k” will be the distance of the balance point (where you can balance the shaft of the club on your finger) to the club head instead of the hand grip.  Fill in the rest of the table 2 below and calculate I again. Table 2 Club I (kg m 2 ) k (m) m (kg) I = m k 2

KIN3202-Biomechanics of Physical Activity 2 Driver 0.0079 0.26 0.118 Iron 0.0048 0.22 0.1 Activity 2: Changing the radius of gyration (k)  For the following activity each member of the group will participate in swinging the golf club. Be careful when using the golf clubs. Make sure you have enough room when swinging and that you do not let go off the golf club while swinging.  Attempt to swing each driver with the same angular velocity between trials while being mindful that for the sensor to record your swing, you will need to swing fully and successfully hit the foam golf ball.  First, once you have calibrated your sensor, swing the driver normally. Record the velocity of your swing in table 3 under the “normal” column.  Next, choke up on the grips by sliding your hands to a higher position on the club than they were for your previous swing. With this positioning, swing the driver and record your velocity in the “choke up” column of table 3.  Finally, flip the club upside down. You will hold it just below the club head with the sensor close to the ground. Swing the club and record the velocity in the “upside down” category. Table 3 Name Normal (velocity) Choke up (velocity) Upside down (velocity) Jim 70 73 97 Dwight 86 91 101 Angela 100 110 122 Michael 54 60 75  Repeat the process above with an iron. Table 4 Name Normal (velocity) Choke up (velocity) Upside down (velocity) Jim 55 60 70 Dwight 78 82 90 Angela 90 97 103 Michael 49 54 60 Questions

KIN3202-Biomechanics of Physical Activity 3 1. Describe what inertia is and compare it to moment of inertia. Inertia is resistance to change in the state of rest or uniform motion, which involves 2 factors, and they are inertial factor and motion factor. Inertial and motion factors combine to create momentum. Moment of inertia is the resistance to change of its state of motion, unless external force is applied to the body. 2. Using the data in table 1, which club had the lower I and why? Using the data in table 1, the club that has the lower I is the driver club, this was figured out by calculating the numbers recorded and getting I for each club. 3. Which measurement (balance point to hand grip or club head) had the lower I and why? Iron had the lower I and this is because after the calculations the number was lower due to it being able to balance the shaft of the club on your finger better. 4. Which condition (normal, chocking up, or upside down) was “easier” to swing and why? From looking at both clubs, upside down was “easier” to swing, and this is because the velocity was higher therefore the speed of it was faster which it can be implied that the swing was easier to go through with than normal or choking up. 5. Which condition (normal, chocking up, or upside down) produced the fastest velocity and why? Upside down produced the fastest velocity; this is because it may have felt lighter doing the swing. The upside down of both clubs had overall higher precents. 6. Does choking up increase velocity? Why or why not? This answer may vary depending on each person but based off the results of this lab, choking up was runner up for fastest velocity, so I would say yes choking up did/can increase velocity, this could be because choking up on the club gives the person swinging more grip to control the club therefore more control over the club can lead to a faster swing. 7. How does I relate to velocity? Inertia relates to velocity by keeping it in motion but at the same velocity or keeping something at the rest state, but does not do so if a force occurs changing its direction or speed 8. Comparing the driver and the club which produced the higher velocity and why? After comparing the results of both clubs and looking at all numbers, the driver had overall higher speeds for each way (normal, choked up, upside down) therefore the driver club produced the higher velocity, this could be due to it being lighter in weight and easier to balance and give the faster swings.

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