Question

Short answer questions:-

1. What is a machine?

2. By giving three examples define non-luminous body.

3. What are the characteristics of image formed in to pinhole camera?

4. What is shadow and write the conditions necessary for formation of shadow.

5. Write two applications of rectilinear propagation of light.

6. Write uses of screws (two).

7. What is umbra & penumbra?

8. Explain input &output energy & principle of machine


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Answer 1

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• What is a machine?

A machine (or mechanical device) is a mechanical structure that uses power to apply forces and control movement to perform an intended action.

• By giving three examples define non-luminous body.

A non-luminous body is an object that does not shines by its own light. It needs a luminous body in its surrounding whose light it can reflect and become visible.

Non luminous bodies are the planets, the moon and objects of daily use such as book, pencil, eraser, paper, etc.

• What are the characteristics of image formed in to pinhole camera?

The image in a pinhole camera is inverted (upside down) as compared to the object. The image in a pinhole camera is real (because it can be formed on a screen). The image in a pinhole camera is of the same colour as the object.

• What is shadow and write the conditions necessary for formation of shadow.

The following three things are required for a shadow to form:

• a source of light.
• an opaque object.
• a screen or surface behind the object.

• Write two applications of rectilinear propagation of light.

The simple applications of rectilinear propagation of light are pin hole camera, formation of shadows and ellipses.

• Write uses of screws (two).

Screws are widely used in threaded fasteners to hold objects together, and in devices such as screw tops for containers, vises, screw jacks and screw presses. Other mechanisms that use the same principle, also called screws, don't necessarily have a shaft or threads.

• What is umbra & penumbra?

During an eclipse, two shadows are cast. The first is called the umbra . It is the dark center of the eclipse shadow. The second shadow is called the penumbra . The penumbra gets larger as it goes away from the sun.

• Explain input &output energy & principle of machine.

• Input

Input refers to the amount of energy put into a device.

• output

Output refers to the amount of energy that comes out.

• Principle

The work output of a machine is equal to the work input. All machines work on the principle that when the effort is smaller than the load, it has to move a greater distance in order to achieve the same work.