Measurement Of TimeIn the beginning, people used calendars to keep a track of years, which were divided into months and days (not exactly what we use today, but something similar). Later, people started keeping track of the time of the day. They started…

Distance Versus Time GraphsGenerally, a vehicle travelling on a road does not travel at a constant speed throughout its journey. If we note the distance travelled by the object at equal intervals of time (like every second or every minute), we will get a…

What are the Different Types of SoundSound can be of different types—soft, loud, pleasant, unpleasant, musical, audible (can be heard), inaudible (cannot be heard), etc. Some sounds may fall into more than one category. For instance, the sound produced w…

Reflection Of SoundSound waves like light waves also get reflected from plane and spherical surfaces. During reflection, sound waves obey the laws of reflections. The reflection of sound from a hard surface can be observed by performing a simple experime…

Speed Of Sound In Various SubstancesSpeed of Sound: The speed of sound is the rate at which sound travels from the sound producing body of our ears. The speed of sound depends on theNature of Material: (or medium) through which it travels. Speed of soun…

What Are The Harmful Effects Of Noise PollutionUnpleasant, discomfort-causing sound from any source is called noise. Sustained presence of harmful, unwanted, or annoying noise in the environment is called noise pollution.Sources of noise pollution Any o…

Sorting Materials Into GroupsPlacing or sorting similar things together is called grouping. Grouping makes it easier for us to find things when we need them.GROUPING ON THE BASIS OF COMMON PROPERTIESObjects are made of different materials. One material …

History Of Transport And Travel In ancient times, people had to walk, use boats or animals like horse to travel from one place to another. They used simple boat and raft made of tree trunks to travel across rivers. Later, invention of the wheel led to th…

How do we convert nuclear energy into usable energy?At electrical power stations, turbines turn their rotors to produce electricity by electromagnetic induction.At a nuclear power station, the energy released by nuclear fission reactions is used to drive…

Advantages and Disadvantages of Electricity GenerationEffects Caused by the Generation of Electricity Table summarises the generation of electricity, the advantages and disadvantages of various energy resources.Energy resourceGeneration of electricityAd…