Question

Classify the following as a type of potential energy or kinetic energy (use the letters K or P)

Answer 1

1. Use these definitions:


i) Kinetic energy (KE) is energy in action in virtue of the motion. KE = (1/2)mv². You can tell there is KE wthen the object is moving.


ii) Potential energy (PE) is a stored energy. You notice the PE once it is transformed into another form of energy, for example into kinetic energy or heat, or light. The maing forms of potential energy are gravitational potential energy (mgh), elastic potential energy (1/2)kx², and chemical potential energy.


2) Answers


1. A bicyclist pedaling up a hill: K

In virtue of the motion (speed) the byciclist has kinetic energy. Neverthelles, the pedalyst also has potential energy, which you could notice if she stops pedaling, because then she would start to go down the hill without pedaling.


2. An archer with his bow drawn : P


The bow will have elastic potential energy in virtue of which the arrow will be throwm as soon as the archer release it.


3. A volleyball player spiking a ball K


The ball will have kinetic energy in virtue of its speed

4. A baseball thrown to second base: K


The baseball will have kinetic energy in virtue of its speed.


5. The chemical bonds in sugar: P


The bonds have stored potential energy. This energy is named chemical energy. When the bonds break they release energy in the form of heat, light or sound.


6. The wind blowing over a tree: K


The wind is moving, so it has kinetic energy. You notice the energy of the wind because it is capable to move the leaves or even the same tree, The same happens when the wind moves the blades of a windmill.


7. Walking down the street: K


When you walk you are moving, so you have speed and that is kinetic energy.


8. Sitting at the top of a tree: P


Sitting on a high place gives you potential energy (mgh). You potentially can suffer an injure if you fall down. The potencial energy transforms into kinetic energy when you fall down.


9. A bowling ball rolling down the alley: K


The ball is rotating and translating. It has angular speed and traslational speed.Both are kinetic energies.


10. A bowling ball sitting on the rack: P


While the ball is on the rack, it has the possibility to fall down. The ball can fall off the rack and hit the floor or your foot. The stored (potential) energy can be transformed into kinetic energy.