1What is energy? Write its SI unit.
2Define mechanical energy and name its kinds.
3Define kinetic energy and potential energy and give two examples of each.
4What factors does kinetic energy depend on? Write it with the relation.
5Write two differences between kinetic energy and potential energy.
6What is transformation of energy? What difficulties would we face if energy could not be transformed?
7The food we eat is a transformed form of sunlight. Explain this statement with reasons.
8Even without eating we can work for a short while, but not for long. Explain both facts in terms of energy.
9Which does more damage in a crash, a slow moving vehicle or a fast moving one, and why?
10Give the reason: in winter, quilts and bedding are spread out in the sun to dry.
11Give the reason: in summer white clothes are more comfortable than black ones.
12What is heat absorption? What does it depend on?
13Explain the importance of heat in daily life.
14Distinguish between a ray and a beam of light.
15Distinguish between the umbra and the penumbra.
16What is a shadow? How many kinds are there? Why is a shadow a different length in the evening and at midday?
17Explain with a diagram that light travels only in a straight line.
18Can we make a camera without a lens? What is it called, and why does the picture in it appear upside down?
19A lighted bulb brightens the room in every direction. How is that possible if light travels only in straight lines?
20Give the reason: special equipment is needed to talk to a friend on the moon.
21What is a wave? How is it produced?
22What is the same and what is different when sound travels through a solid, a liquid and a gas?
23We see the lightning flash first and hear the thunder only afterwards. Why?
24You put your ear against one end of a long wall while a friend taps the other end, and next time you listen without touching it. In which case is the sound heard, and why?
25Water from a roof tank runs out of the tap into a bucket. What transformation of energy has taken place?
26What happens to the height of the picture when the inner tube of a pinhole camera is pulled outwards?
27Can animals living in water hear sounds made outside it? Give the reason.