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Subject: Science, asked on on 30/9/13
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Subject: Science, asked on on 7/12/17
. A person standing near the cliff fires the gun and heared the echo after 1.5 sec . If the speed of sound in air is 340m/sec , how far is person from the cliff? 

3. A sound wave of frequency 5000 Hz travel in air with speed of 350m/sec. Calculatethe wave length. 

4. If u hear thunder 7 sec after u see yhe lightining , how far u from the lighting occurred? 

5. A bat emits ultrasonic wave of frequency 30 Khz..If its speed is 350m/s and bats hear its echo after 0.6 sec after emitting the , find how far is bat from obstacle and wave length of wave? 

6. Meera is standing between two hills.She shouted loudly and hears first echo after 0.5 sec and second echo after 1 sec. what is distance between two hills? 7. If 2000 ripples produced in 5 sec in a pond find time period and frequency of ripples formation. 

8. A man standing in a valley between two parallel mountains fires a gun and hears echo at an interval of 2 s and 3.5s. what is a) the distance between two mountains b) the location of the man with respect to the mountain.

  9. Calculate the wavelength of a sound whose frequency is 220 Hz and speed is 440 in a given medium.
  10. A body is vibrating 6000 times is 1 minute. If the velocity of sound in air is 360 m/s, find 
(i) Frequency in Hz   (ii) wavelength of sound. 
  11. . A stone is dropped from a 500 m tall building into a pond. When is sound splash heard? Given g=10 m/s2 , speed of sound = 340 m/s. 
  12. An echo is heard in 3 sec after the emission of sound. If speed of sound in air is 342 m/s, what is the distance of the reflecting surface from the source?
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Subject: Science, asked on on 15/9/18
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Subject: Science, asked on on 30/4/20
The largest COVID-19 national lockdown in the world has been extended to May 3. As of April 22, India has reported 18?985 confirmed cases and 603 deaths from COVID-19 in 31 states and union territories since its first case on Jan 30. India was quick to close its international borders and enforce an immediate lockdown, which WHO praised as ?tough and timely?. The lockdown has also given the government time to prepare for a possible surge in cases when the pandemic is forecasted to peak in the coming weeks. Still, India's population of 1?3 billion across diverse states, health inequalities, widening economic and social disparities, and distinct cultural values present unique challenges.

Preparedness and response to COVID-19 have differed at the state level. Kerala has drawn on its experience with the Nipah virus in 2018 to use extensive testing, contact tracing, and community mobilisation to contain the virus and maintain a very low mortality rate. It has also set up thousands of temporary shelters for migrant workers. Odisha's exposure to previous natural disasters meant crisis precautions were already in place and have been repurposed. Maharashtra has used drones to monitor physical distancing during lockdown and applied a cluster containment strategy: if three or more patients are diagnosed, all houses within 3 km are surveyed to detect further cases, trace contacts, and raise awareness. Whether this strategy will be successful is still unclear. The premise relies on there not being community transmission, and there is danger of stigmatisation and coercion. But states deserve much of the credit for India's COVID-19 response.

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The government's sudden enforcement of the lockdown seemed hastily prepared and immediately disadvantaged already vulnerable populations. There has been a mass exodus of migrant workers and concerns are rising about starvation among people who work in the informal economy. Implementing public health measures is difficult in places with overcrowded living conditions and inadequate hygiene and sanitation. Non-COVID-19 health services have been disrupted.?Reports?suggest that the government's efforts to provide financial support and a measure of food security to ease these pressures will be insufficient to meet demand. But better planning and communication could have helped avert this crisis.

Rates of testing have been low (0?28 per 1000 people as of April 20). Capacity issues, absence of political will, and operational feasibility have been to blame. However, efforts to reverse the situation are underway as hundreds of thousands of testing kits have become available, and more testing companies and laboratories have been approved. Testing needs to be expanded exponentially as well as strategically as a tool to provide epidemiological evidence. India's response has also been constrained by a shortage of health workers, but this should be remedied by new reforms that would mobilise additional health-care workers from different sources.

One threat to the COVID-19 response in India is the spread of misinformation driven by fear, stigma, and blame. There have been rising levels of violence against health-care workers and stigmatisation of people with or suspected of having COVID-19, which could impede reporting of illness. The pandemic has also been used to fan anti-Muslim sentiment and violence, after a gathering connected to the group Tablighi Jamaat was identified as being responsible for many cases. A welcome initiative to combat fake news is being led by a group of more than 400 multidisciplinary Indian scientists, who have voluntarily formed Indian Scientists' Response to COVID-19 to fight myths and misinformation about the disease.

In India's favour are its young population (65% aged
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