1. List one case in which potential energy becomes kinetic energy and one case in which kinetic energy becomes potential energy.
2. State the law of conservation of energy in your own words.
3. Describe the rise and fall of a thrown basketball by using the concepts of kinetic energy and potential energy.
4. Use the concepts of kinetic energy and potential energy to describe the motion of a child on a swing.
5.Why do we use systems? Explain the difference between an open system, closed system, and isolated system.
Answers
Explanation:
1.
Potential energy to Kinetic energy:
1) Water flowing from water storage tanks
2) Kinetic energy of an arrow released from a bow
3)Kinetic energy of an object falling from height
Kinetic energy to Potential energy:
1)A projectile when it reaches the top most point converts part of its initial kinetic energy to potential energy
2) A pendulum has kinetic energy at the lowest point which is converted to potential energy at the top most point
3) Spring or Elastic can be stretched to store energy as it wants to return to rest
2.
The law of conservation of energy states that energy can neither be created nor destroyed - only converted from one form of energy to another. This means that a system always has the same amount of energy, unless it's added from the outside. This is particularly confusing in the case of non-conservative forces, where energy is converted from mechanical energy into thermal energy, but the overall energy does remain the same. The only way to use energy is to transform energy from one form to another.
3.
The player throws the basketball in the air with some initial velocity.This kinetic energy is used to do work against the force of gravity and the ball rises to its top most point.At this point the kinetic energy is converted into potential energy.Using this potential energy the ball descends converting the potential energy to kinetic energy and reaches the ground with the same initial velocity as energy remains conserved
4.
They need to push from time to time, because the energy is dying down, and gravity is holding them to the ground. You need an arsenal of energy (body) to go against gravity.
5.
There are three types of systems in thermodynamics: open, closed, and isolated.
An open system can exchange both energy and matter with its surroundings. The stovetop example would be an open system, because heat and water vapor can be lost to the air.
A closed system, on the other hand, can exchange only energy with its surroundings, not matter. If we put a very tightly fitting lid on the pot from the previous example, it would approximate a closed system.
An isolated system is one that cannot exchange either matter or energy with its surroundings. A perfect isolated system is hard to come by, but an insulated drink cooler with a lid is conceptually similar to a true isolated system. The items inside can exchange energy with each other, which is why the drinks get cold and the ice melts a little, but they exchange very little energy (heat) with the outside environment.