Question

checking concepts

1. define work in terms of energy.
2. how do you find an objects mechanical energy?
3. for each of the following, decide which forms of energy are present: a walnut falls from a tree; a candle burns; a spring is stretched.
4. an eagle flies from its perch in a tree to the ground to capture and eat its prey. describe its energy transformations.
5. how does energy become stored in a fossil fuel? what kind of energy is stored?

Explanation:

1. Work is the transfer of energy that occurs when a force acts on an object and causes it to move. When work is done on an object, energy is transferred to the object, and when work is done by an object, energy is transferred from the object.
2. An object's mechanical energy is the sum of its kinetic energy (energy of motion) and its potential energy (stored energy due to position or state). So, Mechanical Energy = Kinetic Energy + Potential Energy.

13.

• A walnut falling from a tree has kinetic energy (due to its motion) and gravitational - potential energy (due to its height above the ground). As it falls, its gravitational - potential energy is converted into kinetic energy.
• A burning candle has chemical energy (stored in the wax and oxygen) which is converted into thermal energy (heat) and light energy.
• A stretched spring has elastic - potential energy (stored due to its deformation).

1. When an eagle flies from its perch to the ground to capture prey:

• Initially, it has gravitational - potential energy due to its height on the perch. As it starts to fly down, this potential energy is converted into kinetic energy (energy of motion). When it catches the prey, some of its kinetic energy is used to do work on the prey.

1. Energy becomes stored in a fossil fuel through the process of photosynthesis by plants millions of years ago. Plants convert solar energy into chemical energy (stored in carbohydrates). When the plants and other organisms die and are buried under sediment, over time, they are transformed into fossil fuels. The kind of energy stored in fossil fuels is chemical energy.

Answer:

1. Work is the transfer of energy due to a force causing displacement.
2. Mechanical energy = Kinetic energy + Potential energy.
3. Walnut falling: Kinetic and gravitational - potential energy; Candle burning: Chemical, thermal, and light energy; Stretched spring: Elastic - potential energy.
4. Gravitational - potential energy is converted into kinetic energy during flight, and some kinetic energy is used to do work on the prey.
5. Energy is stored through photosynthesis and is chemical energy.