Q4 of 26 Page 28

Study the following activity and answer the questions.

1. Take two aluminium channels of different lengths.


2. Place the lower ends of the channels on the floor and hold their upper ends at the same height.


3. Now take two balls of the same size and weight and release them from the top end of the channels. They will roll down and cover the same distance.




What is the form of the eventual total energy of the balls?

Total energy of the ball is sum of kinetic energy and potential energy, kinetic energy depends upon velocity of body, potential energy depends upon position of ball (height from surface of earth in gravitational potential energy), they keep varying but their sum i.e. total energy always remains constant.

Now eventually initially ball was at rest at a height h above the surface of earth so form of energy was potential energy now as we know the Relation for Potential energy of an object of mass m due to earth’s gravity (g is acceleration due to gravity) held at an height h above ground is


P.E. = mgh


More from this chapter

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4

Study the following activity and answer the questions.

1. Take two aluminium channels of different lengths.


2. Place the lower ends of the channels on the floor and hold their upper ends at the same height.


3. Now take two balls of the same size and weight and release them from the top end of the channels. They will roll down and cover the same distance.




As the balls roll down which energy is converted into which other form of energy?

 4

Study the following activity and answer the questions.

1. Take two aluminium channels of different lengths.


2. Place the lower ends of the channels on the floor and hold their upper ends at the same height.


3. Now take two balls of the same size and weight and release them from the top end of the channels. They will roll down and cover the same distance.




Why do the balls cover the same distance on rolling down?

 4

Study the following activity and answer the questions.

1. Take two aluminium channels of different lengths.


2. Place the lower ends of the channels on the floor and hold their upper ends at the same height.


3. Now take two balls of the same size and weight and release them from the top end of the channels. They will roll down and cover the same distance.




Which law related to energy does the above activity demonstrate? Explain.

 5

Solve the following examples.

An electric pump has 2 kW power. How much water will the pump lift every minute to a height of 10 m?