Take one fast sprinter with a pole, add in gravitational potential energy converted to kinetic energy, and you have the physics for a successful pole vault!
Kinetic energy is the energy of motion. All moving objects, including the wind, roller coasters or our sprinting pole vaulter, have kinetic energy. The faster an object or a person moves, the more kinetic energy it has. This explains why a car hitting a wall at 5 miles per hour will just dent the bumper, but when it hits a wall at 40 miles an hour, the car is totaled. The greater (faster) the motion, the more kinetic energy an object has.
Next comes gravitational potential energy, or the energy due an object’s position or place. It’s the energy stored in an object as a result of its height or vertical position and the force of gravity. There is a direct relationship between height and gravitational potential energy: the taller or higher an object, the greater the gravitational potential energy. Since gravitational potential energy is directly proportionate to its height, doubling the height will also double an object’s gravitational potential energy. A roller coaster car sitting motionless before a 100-foot drop has double the gravitational potential energy of a roller coaster car with at a 50-foot drop.
Here’s an example of kinetic energy and gravitational potential energy acting on an object. You just placed a book on a low table. The unmoving book has gravitational potential energy. You can release this gravitational potential energy by knocking the book off the table. As the book falls, its gravitational potential energy is converted into kinetic (motion) energy. When the book hits the floor, all motion stops and the kinetic energy is converted into heat and sound upon impact. This time, however, place the book on top of a table or shelf 3 times higher to increase the gravitational potential energy 3 fold. Now knock it off. Since the book is falling from a height 3 times greater than the low shelf, the book has more time to build greater kinetic energy and will hit the floor with a much louder sound and greater impact. Increased height means increased gravitational potential energy and greater (faster) kinetic energy. This also explains why a roller coaster having a hundred foot drop is a lot more exciting than one with only a fifty foot drop!
Our pole vaulter is going to be tall and lean to achieve the maximum gravitational potential energy and kinetic energy. A tall sprinter can hold the pole higher to achieve a greater gravitational potential energy than a shorter sprinter. A lean sprinter also has greater muscle mass to run faster and jump higher to achieve maximum kinetic energy.
To achieve maximum take off, our vaulter will use a pole that’s lightweight yet strong enough to withstand incredible forces without cracking or breaking. To achieve this, poles are made by wrapping thin sheets of fiberglass around a pole pattern to produce a semi-bent pole that bends more easily under the force of a vaulter’s take off. Recently, manufacturers have added carbon fibers to the fiberglass to create a lighter pole with maximum bend.
Now let’s see how gravitational potential energy, kinetic energy, and the sprinter and pole come together to create a successful pole vault.
Our sprinter is at the starting line, and at the signal, begins his/her sprint down the track. The sprinter carries the pole as upright as possible to achieve maximum gravitational potential energy. The sprinter also holds his/her torso upright to further build up his/her gravitational potential energy. The sprinter uses long strides to build up speed running to the pit (the area where the bar and mats are waiting), then increases the stride frequency as he/she approaches the bar. The faster the vaulter sprints toward the bar, the more kinetic energy is built up.
The last three steps are designed to maximize the gravitational potential energy of the sprinter’s upright torso and pole with the kinetic energy of sprinting. The vaulter raises his/her arms over head while at the same time dropping the pole into the box (a trapezoidal indentation where vaulters plant their poles). This causes the kinetic energy of sprinting to transform and be stored in the pole as additional gravitational stored energy. On the final step, the vaulter jumps up to attain maximum vertical height. As the pole slides into the back of the box, the pole bends, and the gravitational potential energy stored within the pole is released as kinetic energy, hurtling our pole vaulter up into the air. As the pole straightens, the kinetic energy catapults the vaulter up and over the bar. The vaulter then descends back to the ground, and any remaining kinetic energy is released as sound or is absorbed by the mat.
Our pole vaulter then gets to his/her feet and enjoys the spectator’s applause and cheers in their appreciation of a vault well done!
