Mechanical Energy
Define Mechanical Energy
It is the energy possessed by a body due its state of rest or motion.
The lid of a kettle moving up due to _______ is an example of _________ energy.
50m per blank
steam, heat
In a photo voltaic cell, light energy gets converted into ___________ energy.
electrical
Define energy.
Energy is defined as the capacity to do work.
Name the two factors affecting the potential energy of a body placed at a height.
100m per factor
- the mass of the body
- it' height above the ground
What are 8 forms of energy?
100m for 4
Mechanical, heat, light, chemical, sound, magnetic, electrical and atomic/nuclear energy.
State the law of conservation of energy.
The total energy is always conserved in each transformation of energy.
What are the 2 units of energy? Also, what is their relation?
150m - units
50m - relation
The two units of energy are joule (J) and calorie (cal).
1 cal = 4.18 J
Define Kinetic energy and Potential energy and give examples of each.
200m - definitions
100m- examples
Kinetic Energy: Kinetic energy of a body is the energy possessed by it due to its state of motion.
ex. the bob of a swinging pendulum
Potential Energy: Potential energy of a body is the energy possessed by it due to its state of rest.
ex. a stretched rubber catapult
pg. 39, 40
Define, explain and give an example for any energy form of your choice (except mechanical energy)
100m - define
150m- explain
50m- example
pg. 37, 38
Give any 3 examples of energy conversions.
100m for each
mixer grinder - electrical to mechanical
generator - mechanical to electrical
biogas - chemical to heat
pg. 43
What is the relationship between work and energy? (2 pts)
150m per point
- to do more amount of work, you need more energy
- the work done on a body in changing its state is said to be the energy possessed by the body
Name the two factors affecting the kinetic energy of a moving body and explain an activity to support your answer.
100m- factors
300m- activity
Factors affecting Kinetic Energy:
- the mass of the body
- the speed of the body
Activity:
Take a hockey stick and a ball. Place the ball on the ground and gently hit it with the stick. You notice the the ball moves slowly. Now hit the ball very hard with the stick. You notice that the ball travels fast and covers a longer distance. Thus, the more force applied on the ball, the more the gain in kinetic energy of the ball.
State 2 uses (each) for atomic energy and magnetic energy.
100m per use
Atomic energy:
- it can generate electricity through atomic reactors
- it is used for destructive purposes like atom bombs and other weapons for war
Magnetic Energy:
- electromagnets are used to separate iron scrap from heaps of waste material
- an electric motor, which is used to run fans and other household machines is provided with a magnet.
Fill in the blanks
i) A rollercoaster operates on the principle of ___________________.
ii) In the absence of _________, the total sum of the potential energy and the kinetic energy remains constant.
iii) In a microphone, ____________ energy changes into ___________ energy.
100m per blank
i) conservation of energy
ii) friction
iii) sound, electrical
Explain the production of hydroelectricity in your own words.
pg. 45
main points:
- water in motion in a river/sea has kinetic energy
- the flowing water of the water body is collected in a dam at high altitude
-the stored water has potential energy
- when this water falls on the water turbine, the energy is converted into kinetic energy which is transferred to the turbine blades
- as the turbine rotates, it rotates the armature of the dynamo to produce electricity.
Describe the conversion of potential energy into kinetic energy with the help of an example.
A wound up watch spring has potential energy because of its wound up state. As the spring unwinds itself, the potential energy changes into kinetic energy. This kinetic energy allows the movement of the arms of the watch.
pg. 41
State true or false
i) Our food possesses chemical energy, allowing us to do work.
ii) Steam energy possesses chemical energy and is capable of doing work.
iii) A strong beam of light is incapable of moving electrons.
iv) Electric energy can be converted into other forms of energy.
125m per question
True - i, iv
False - ii, iii
HOTS : What is dissipation of energy?
In transformation of energy when one form of energy is changed to another useful form of energy, a part of energy gets converted with the non-useful form which is called dissipation of energy.
Define the following:
i) Hydroelectricity
ii) Electrical energy
250m per definition
i) Hydroelectricity is the electricity obtained from the energy possessed by flowing water.
ii) Electrical energy is the energy we get when we use a battery, electricity supplied by the electricity board or a generator.