Energy Flashcards
(23 cards)
Define work
Work is said to be done only when a force acts on an object and makes it move through a distance in the direction of force.
The necessary conditions for work to be done are?
- Force must act on an object
1. The point where force is applied should move in the direction of the force.
Define displacement
The distance moved in the direction of force is called displacement
Name the unit of force, distance and work.
Newton (N), metre (m), joule (J).
What is the formula of work done?
Work done= force×displacement.
OR
1 joule= 1 Newton×1 metre
Define energy and name its SI unit
The capacity to do work is called energy. The SI unit of energy is also joule.
Define mechanical energy
The energy possessed by an object by virtue of its position or state of motion.
Define Kinetic energy
The energy possessed by an object by virtue of its motion. Example: a moving ball, flowing wind, galloping horse; all posses kinetic energy.
The formula of kinetic energy is?
KE=½mv²
M is mass and v is velocity
Define potential energy
The energy stored in an object by virtue of its position or a change in shape. Example: water stored in a tank, stretched string of a bow, all posses potential energy.
Define gravitational energy
The energy possessed by a body due to its height above the ground. For example rocks that rest on top of a hill have gravitational potential energy.
Define elastic potential energy
The energy stored in the body from the work done by stretching, bending or compressing the body is called elastic potential energy. Example the wound up spring of clock is an example of a body that posses elastic potential energy.
What is the formula of potential energy?
PE= m×g×h
M is mass, g is gravity and h is height
What is transformation of energy?
Conversion of energy from one form to another is called transformation of energy.
What does the law of conservation of energy state?
The law of conservation of energy states that energy can neither be created nor destroyed. It can only be transformed from one form to another.
Give examples of law of conservation of energy.
- When we throw a ball from a height, potential energy changes to kinetic energy.
- On a rollercoaster ride, potential energy changes to kinetic energy, which again changes to potential energy. But the amount of energy remains the same at every point.
What is an energy chain?
The process of conversion of solar energy into electrical energy.
How is sun the ultimate source of energy?
Sun is the ultimate source of energy. There are different ways from which the energy of the sun reaches us. The following diagram explains:
Solar energy>chemical energy>heat energy>electrical energy
OR
Solar energy> potential energy>kinetic energy>electrical energy.
Define power
The rate if doing work or the rate of using energy.
What is the SI unit of power?
Joule/second (J/s), known as watt (W).
Differentiate between energy and power.
Energy:
- Capacity of doing work
- It can be stored.
- Can be transformed
- SI unit is joule.
Power:
- Rate of doing work
- Cannot be stored
- cannot be transformed.
- SI unit is Watt.
Explain an activity to show that potential energy stored depends on height.
Suspend the pendulum from the iron stand. Place a matchbox near the bob of the pendulum. Pull the bob and position it to a little higher level than the matchbox, and then release the bob. You will observe that when the bob hits the matchbox, it displaces it. This proves that potential energy stored in am object depends upon the height of the object.
Explain an activity to show transformation of energy
Suspend the bob from an iron stand. Pull the bob to its maximum height. Understand that by pulling the bob you’re giving it potential energy. At maximum height, it has maximum potential energy and zero kinetic energy. But as you release the bob, it moves down and potential energy changed to kinetic energy. When the bob reaches the bottom of the string, it posses maximum kinetic energy and zero potential energy.
