A boat which has a speed of 5 km/hr in still water crosses a river of width 1 km along the shortest possible path in 15 minutes. The velocity of the river water in km/hr is
- (a)1
- (b)3
- (c)4
- (d)41
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Official answer(b) 3
Other questions on Physics
In a pressure cooker, the temperature at which the food is cooked depends mainly upon which of the following? 1. Area of the hole in the lid 2. Temperature of the flame 3. Weight of the lid Select the correct answer using the code given below.
- (a)1 and 2 only
- (b)2 and 3 only
- (c)1 and 3 only
- (d)1, 2 and 3
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Official answer(c) 1 and 3 only
Consider the following phenomena : 1. Light is affected by gravity. 2. The Universe is constantly expanding. 3. Matter warps its surrounding space-time. Which of the above is/are the prediction/predictions of Albert Einstein's General Theory of Relativity, often discussed in media ?
- (a)1 and 2 only
- (b)3 only
- (c)1 and 3 only
- (d)1, 2 and 3
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Official answer(d) 1, 2 and 3
In the context of modern scientific research, consider the following statements about ‘IceCube’, a particle detector located at South Pole, which was recently in the news : 1. It is the world’s largest neutrino detector, encompassing a cubic kilometre of ice. 2. It is a powerful telescope to search for dark matter. 3. It is buried deep in the ice. Which of the statements given above is/are correct?
- (a)1 only
- (b)2 and 3 only
- (c)1 and 3 only
- (d)1, 2 and 3
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Official answer(d) 1, 2 and 3
Ball bearings are used in bicycles, cars, etc., because
- (a)the actual area of contact between the wheel and axle is increased
- (b)the effective area of contact between the wheel and axle is increased
- (c)the effective area of contact between the wheel and axle is reduced
- (d)None of the above statements is correct
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Official answer(c) the effective area of contact between the wheel and axle is reduced
Consider the following phenomena: 1. Size of the sun at dusk 2. Colour of the sun at dawn 3. Moon being visible at dawn 4. Twinkle of stars in the sky 5. Polestar being visible in the sky Which of the above are optical illusions?
- (a)1, 2 and 3
- (b)3, 4 and 5
- (c)1, 2 and 4
- (d)2, 3 and 5
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Official answer(c) 1, 2 and 4
Rainbow is produced when sunlight falls on drops of rain. Which of the following physical phenomena are responsible for this? 1. Dispersion 2. Refraction 3. Internal reflection Select the correct answer using the codes given below.
- (a)1 and 2 only
- (b)2 and 3 only
- (c)1 and 3 only
- (d)1, 2 and 3
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Official answer(d) 1, 2 and 3